WO2014195972A1 - ONE STEP PROCESS FOR REGIOSELECTIVE SYNTHESIS OF α-ACYLOXY CARBONYLS - Google Patents

ONE STEP PROCESS FOR REGIOSELECTIVE SYNTHESIS OF α-ACYLOXY CARBONYLS Download PDF

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WO2014195972A1
WO2014195972A1 PCT/IN2014/000374 IN2014000374W WO2014195972A1 WO 2014195972 A1 WO2014195972 A1 WO 2014195972A1 IN 2014000374 W IN2014000374 W IN 2014000374W WO 2014195972 A1 WO2014195972 A1 WO 2014195972A1
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nitrobenzoate
oxo
phenylethyl
oxoethyl
nmr
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Arumugam Sudalai
Rambabu REDDI
Pushpa MALEKAR
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Council of Scientific and Industrial Research CSIR
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Council of Scientific and Industrial Research CSIR
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    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07F—ACYCLIC, CARBOCYCLIC OR HETEROCYCLIC COMPOUNDS CONTAINING ELEMENTS OTHER THAN CARBON, HYDROGEN, HALOGEN, OXYGEN, NITROGEN, SULFUR, SELENIUM OR TELLURIUM
    • C07F7/00—Compounds containing elements of Groups 4 or 14 of the Periodic Table
    • C07F7/02—Silicon compounds
    • C07F7/08—Compounds having one or more C—Si linkages
    • C07F7/18—Compounds having one or more C—Si linkages as well as one or more C—O—Si linkages
    • C07F7/1804—Compounds having Si-O-C linkages
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C67/00—Preparation of carboxylic acid esters
    • C07C67/39—Preparation of carboxylic acid esters by oxidation of groups which are precursors for the acid moiety of the ester
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C205/00—Compounds containing nitro groups bound to a carbon skeleton
    • C07C205/49—Compounds containing nitro groups bound to a carbon skeleton the carbon skeleton being further substituted by carboxyl groups
    • C07C205/57—Compounds containing nitro groups bound to a carbon skeleton the carbon skeleton being further substituted by carboxyl groups having nitro groups and carboxyl groups bound to carbon atoms of six-membered aromatic rings of the carbon skeleton
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07D—HETEROCYCLIC COMPOUNDS
    • C07D213/00—Heterocyclic compounds containing six-membered rings, not condensed with other rings, with one nitrogen atom as the only ring hetero atom and three or more double bonds between ring members or between ring members and non-ring members
    • C07D213/02—Heterocyclic compounds containing six-membered rings, not condensed with other rings, with one nitrogen atom as the only ring hetero atom and three or more double bonds between ring members or between ring members and non-ring members having three double bonds between ring members or between ring members and non-ring members
    • C07D213/04—Heterocyclic compounds containing six-membered rings, not condensed with other rings, with one nitrogen atom as the only ring hetero atom and three or more double bonds between ring members or between ring members and non-ring members having three double bonds between ring members or between ring members and non-ring members having no bond between the ring nitrogen atom and a non-ring member or having only hydrogen or carbon atoms directly attached to the ring nitrogen atom
    • C07D213/60—Heterocyclic compounds containing six-membered rings, not condensed with other rings, with one nitrogen atom as the only ring hetero atom and three or more double bonds between ring members or between ring members and non-ring members having three double bonds between ring members or between ring members and non-ring members having no bond between the ring nitrogen atom and a non-ring member or having only hydrogen or carbon atoms directly attached to the ring nitrogen atom with hetero atoms or with carbon atoms having three bonds to hetero atoms with at the most one bond to halogen, e.g. ester or nitrile radicals, directly attached to ring carbon atoms
    • C07D213/78—Carbon atoms having three bonds to hetero atoms, with at the most one bond to halogen, e.g. ester or nitrile radicals
    • C07D213/79—Acids; Esters
    • C07D213/803—Processes of preparation
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07D—HETEROCYCLIC COMPOUNDS
    • C07D307/00—Heterocyclic compounds containing five-membered rings having one oxygen atom as the only ring hetero atom
    • C07D307/02—Heterocyclic compounds containing five-membered rings having one oxygen atom as the only ring hetero atom not condensed with other rings
    • C07D307/34—Heterocyclic compounds containing five-membered rings having one oxygen atom as the only ring hetero atom not condensed with other rings having two or three double bonds between ring members or between ring members and non-ring members
    • C07D307/56—Heterocyclic compounds containing five-membered rings having one oxygen atom as the only ring hetero atom not condensed with other rings having two or three double bonds between ring members or between ring members and non-ring members with hetero atoms or with carbon atoms having three bonds to hetero atoms with at the most one bond to halogen, e.g. ester or nitrile radicals, directly attached to ring carbon atoms
    • C07D307/60—Two oxygen atoms, e.g. succinic anhydride
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07D—HETEROCYCLIC COMPOUNDS
    • C07D309/00—Heterocyclic compounds containing six-membered rings having one oxygen atom as the only ring hetero atom, not condensed with other rings
    • C07D309/16—Heterocyclic compounds containing six-membered rings having one oxygen atom as the only ring hetero atom, not condensed with other rings having one double bond between ring members or between a ring member and a non-ring member
    • C07D309/28—Heterocyclic compounds containing six-membered rings having one oxygen atom as the only ring hetero atom, not condensed with other rings having one double bond between ring members or between a ring member and a non-ring member with hetero atoms or with carbon atoms having three bonds to hetero atoms with at the most one bond to halogen, e.g. ester or nitrile radicals, directly attached to ring carbon atoms
    • C07D309/30—Oxygen atoms, e.g. delta-lactones

Definitions

  • the present invention relates to a regioselective one step process for synthesis of a- acyloxy carbonyl compounds. Particularly, present invention discloses a regioselective one step process for synthesis of a-acyloxy carbonyl compounds from alkenes.
  • a-acyloxy carbonyls are often found as the key structural motif for many natural products with interesting biological activities and synthetic therapeutics, refer . P. A. Levine, A. Walti, Org. Synth. Coll. Vol. II 1943, 5. These compounds are the potential starting materials for the pfitzinzer reaction in the synthesis of quinoline salicylic acids and their further functional ization results in various biologically active natural products.
  • the acyl groups can serve as useful protecting groups for the hydroxyl functions in a-hydroxy carbonyls. Their importance is reflected in the extensive synthetic research directed toward introducing acyloxy group in a chemo, regio, stereo and enantioselective manner.
  • US 6,384,265 discloses method for stereoselectively producing an alpha-acyloxy carbonyl compound from an enol ester epoxide comprising contacting the enol ester epoxide With a chiral acid catalyst under conditions sufficient to stereoselectively produce the alpha- acyloxy carbonyl compound With inversion of stereochemistry.
  • US 2003/0083376 discloses depot preparations comprising at least one compound of the formula iven below.
  • Rl, R3 and R4, independently of one another, are an organic radical having 1 to 30 carbon atoms;
  • R2 is hydrogen or an organic radical having 1 to 30 carbon atoms, and the compound of the formula given above, after hydrolysis or enzymatic cleavage, releases an alcohol and a carboxylic acid in addition to the aldehyde or ketone.
  • US 5,084,584 discloses a process for producing an a-acyloxy-a, ⁇ unsaturated carbonyl comprising bringing a propargyl ? ester into contact with a platinum group metal compound catalyst in the presence of oxygen and/or a peroxide.
  • US 8,143,423 dicloses a process for preparing hydroxamic acids.
  • the process comprises reacting an aldehyde with a nitroso compound in the presence of a N-heterocyclic carbene (NHC) catalyst.
  • N-heterocyclic carbene (NHC) catalyst Prior art processes for synthesis of a-acyloxy carbonyls are catalysed by metals, including the direct oxidative coupling of carbonyl compounds with toxic heavy metal oxidants namely Pb(OAc) 4; TI(OAc) 3 , ,Mn(OAc) 3 , thus providing environmentally unfriendly processes.
  • Main objective of the present invention is to provide a one step, one pot process for synthesis of ⁇ -acyloxy carbonyls.
  • Scheme 1 represents NHC catalyzed oxidative functionalization of alkenes with aldehydes for synthesis of a-acyloxy carbonyls.
  • present invention provides a single-step, one pot process for preparation of a-acyloxy carbonyl compound of general formula (I)
  • R is selected from H, alkyl, aryl, Bn;
  • Ar is selected from substituted aromatic, unsubstituted aromatic or heteroaromatic;
  • R and Rl optionally can combine to form a ring structure;
  • N-Heterocyclic carbene catalyst is selected from the group consisting of IVa-IVf, preferably IV a.
  • halogen source is selected from the group consisting of N-bromo succinamide (NBS), N-iodo succinamide NIS or N-chloro succinamide NCS, preferably NBS.
  • solvent used is di-methyl sulfoxide
  • yield of the compound of general formula 1 is in the range of 70 to 92%.
  • Present invention provides a one step, one pot process for the synthesis of a-acyloxy carbonyl compounds with regio selectivity, wherein the starting material is an alkene.
  • the process leads to novel ⁇ -acyloxy carbonyl compounds that may be used as key structural motif for synthesis of useful, therapeutically active compounds.
  • the present invention provides a single-step, one pot process for the preparation of a- ac loxy carbonyl compounds of general formula (I)
  • R H, alkyl, aryl or Bn;
  • R l H, alkyl, aryl, -CH 2 OTBS, -CH 2 OBn, -OR or OMOM;
  • Ar aromatic or heteroaromatic;
  • N-Heterocyclic carbene catalyst is selected from:
  • Halogen source is selected from N-bromo succinamide (NBS), N-iodo succinamide (NIS) or N-chloro succinamide (NCS) and preferably NBS.
  • the present invention provides a process for the preparation of a-acyloxy carbonyl compounds of formula (II), wherein the NHC catalysts is preferably IVa to IVd with yields greater than 50%.
  • the present invention provides a process with options of aldehydes to provide a- acyloxy carbonyl with high regioselectivity yield greater than 70% as shown in Table 2.
  • the present invention provides various a-acyloxy carbonyls synthesized by varying the alkenes (III), with >70% yield as shown in Table 3.
  • Ph-CH CH-CH 2 -OTBS (Hi) 28 Ig 92
  • a new catalytic regio selective method for the preparation of acyloxy carbonyl products in preparative yield from a variety of olefins including aromatic, aliphatic and electron rich at ambient conditions is disclosed.
  • Tjhis method is simple, milder and the reagents used are cheap and easy to handle. The process avoids metal catalysts.

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
  • Low-Molecular Organic Synthesis Reactions Using Catalysts (AREA)

Abstract

A regioselective N-Heterocyclic Carbene (NHC) catalyzed one step process for high yield synthesis of α-acyloxy carbonyl compounds is disclosed.

Description

"ONE STEP PROCESS FOR REGIOSELECTIVE SYNTHESIS OF a-ACYLOXY
CARBONYLS"
FIELD OF THE INVENTION
The present invention relates to a regioselective one step process for synthesis of a- acyloxy carbonyl compounds. Particularly, present invention discloses a regioselective one step process for synthesis of a-acyloxy carbonyl compounds from alkenes.
BACKGROUND AND PRIOR ART OF THE INVENTION
a-acyloxy carbonyls are often found as the key structural motif for many natural products with interesting biological activities and synthetic therapeutics, refer . P. A. Levine, A. Walti, Org. Synth. Coll. Vol. II 1943, 5. These compounds are the potential starting materials for the pfitzinzer reaction in the synthesis of quinoline salicylic acids and their further functional ization results in various biologically active natural products. The acyl groups can serve as useful protecting groups for the hydroxyl functions in a-hydroxy carbonyls. Their importance is reflected in the extensive synthetic research directed toward introducing acyloxy group in a chemo, regio, stereo and enantioselective manner.
US 6,384,265 discloses method for stereoselectively producing an alpha-acyloxy carbonyl compound from an enol ester epoxide comprising contacting the enol ester epoxide With a chiral acid catalyst under conditions sufficient to stereoselectively produce the alpha- acyloxy carbonyl compound With inversion of stereochemistry.
US 2003/0083376 discloses depot preparations comprising at least one compound of the formula iven below.
Figure imgf000002_0001
in which Rl, R3 and R4, independently of one another, are an organic radical having 1 to 30 carbon atoms; R2 is hydrogen or an organic radical having 1 to 30 carbon atoms, and the compound of the formula given above, after hydrolysis or enzymatic cleavage, releases an alcohol and a carboxylic acid in addition to the aldehyde or ketone. US 5,084,584 discloses a process for producing an a-acyloxy-a, β unsaturated carbonyl comprising bringing a propargyl ? ester into contact with a platinum group metal compound catalyst in the presence of oxygen and/or a peroxide.
US 8,143,423 dicloses a process for preparing hydroxamic acids. The process comprises reacting an aldehyde with a nitroso compound in the presence of a N-heterocyclic carbene (NHC) catalyst. Prior art processes for synthesis of a-acyloxy carbonyls are catalysed by metals, including the direct oxidative coupling of carbonyl compounds with toxic heavy metal oxidants namely Pb(OAc)4; TI(OAc)3, ,Mn(OAc)3, thus providing environmentally unfriendly processes.
Some processes replaced heavy metal salts with stoichiometric use of N-methyl- Oacylhydroxylamines, but preparation of N-methyl-Oacylhydroxylamines is not an easy process, Also, this is needed in stoichiometric quantities to lead to the desired a-acyloxy carbonyls.
Other prior art processes use harsh conditions for synthesis of desired compounds, making them both economically and environmentally non friendly. Some reports indicate the use of halo substituted carbonyls ie a-halo carbonyls as tarting materials, which are not commercially available, and therefore will have, to be synthesized. This results in long evolving methods of synthesis of desired compounds.
Thus there is a need in the art to provide a simple, environmentally friendly process for synthesis of α-acyloxy carbonyls, such that the process provides a high degree of regio selectivity.
OBJECTS OF THE INVENTION
Main objective of the present invention is to provide a one step, one pot process for synthesis of α-acyloxy carbonyls.
Another objective of the invention is to provide a one step, one pot process for synthesis of α-acyloxy carbonyls with high degree of regio selectivity. Yet another objective of the present invention is to provide an environmentally friendly process conducted in mild conditions with easily available starting compounds. BRIEF DESCRIPTION OF THE DRAWING
Scheme 1 represents NHC catalyzed oxidative functionalization of alkenes with aldehydes for synthesis of a-acyloxy carbonyls.
SUMMARY OF THE INVENTION
Accordingly, present invention provides a single-step, one pot process for preparation of a-acyloxy carbonyl compound of general formula (I)
Figure imgf000004_0001
General formula (I)
wherein R is selected from H, alkyl, aryl, Bn; R1 is selected from H, alkyl, substituted aryl, unsubstituted aryl -CH2OTBS (TBS=Tertiary butyl silyl), -CH2OBn, -OR, OMOM (Methoxy methelene); Ar is selected from substituted aromatic, unsubstituted aromatic or heteroaromatic; R and Rl optionally can combine to form a ring structure;
comprising the steps of:
i. reacting alkene of formula (III) with an aldehyde of formula (IV)
Figure imgf000004_0002
(II) (III)
in the presence of a N -Heterocyclic carbene catalyst (NHC), a halogen source, tri-ethyl amine and a solvent in oxygen atmosphere at a temperature in the range of 15-30°C by stirring for period in the range of 10-50 hours to obtain compound of general formula (I); wherein R is selected from H, alkyl, aryl, Bn; R1 is selected from H, alkyl, substituted aryl, unsubstituted aryl -C¾OTBS (TBS=Tertiary butyl silyl), -CH2OBn, -OR, OMOM (Methoxy methelene); Ar is selected from substituted aromatic, unsubstituted aromatic or heteroaromatic. In an embodiment of the present invention, N-Heterocyclic carbene catalyst is selected from the group consisting of IVa-IVf, preferably IV a.
IVa IVb, ,IVc IVd IVe IVf
Figure imgf000005_0001
wherein for IVb, Ar = 2,4,6-(CH3)3C6H2; for IVc, Ar = 2,6-iP¾C6H3
In another embodiment of the present invention, halogen source is selected from the group consisting of N-bromo succinamide (NBS), N-iodo succinamide NIS or N-chloro succinamide NCS, preferably NBS.
In yet another embodiment of the present invention, solvent used is di-methyl sulfoxide
In yet another embodiment of the present invention, yield of the compound of general formula 1 is in the range of 70 to 92%.
In yet another embodiment of the present invention, representative compound of general formula I are:
2-Oxo-2 -phenylethyl 4-nitrobenzoate (la);
2-(4-Methylphenyl)-2-oxoethyl 4-nitrobenzoate (lb);
2-(4-Bromophenyl)-2-oxoethyl 4-nitrobenzoate (Ic);
2-(4-Fluorophenyl)-2-oxoethyl 4-nitrobenzoate (Id);
2-(4-Acetoxyphenyl)-2-oxoethyl 4-nitrobenzoate (Ie);
2-(3, 4 Dimethoxyphenyl)-2-oxoethyl 4-nitrobenzoate (If);
1 -Oxo-2, 3-dihydro- 1 H-inden-2-yl 4-nitrobenzoate (Ig);
2- Oxo-l,2-diphenyl ethyl 4-nitrobenzoate (Ih);
1 -Oxo- 1 -phenylpropan-2-y 14-nitrobenzoate (Ii) ;
3- ((Tert-butyldimethylsilyl)oxy)-l-oxo-l-phenylpropan-2-yl 4-nitro benzoate (Ij);
3-(Benzyloxy)-2-oxopropyl 4-nitrobenzoate (Ik);
2-Oxooctyl 4-nitrobenzoate (II);
2-Oxodecyl 4-nitrobenzoate (Im); - RMD/NEH/CSIR-49
2-Oxo-4-phenylbutyl 4-nitrobenzoate (In);
2-Ethoxy-2-oxoethyl 4-nitrobenzoate (Io);
2-Oxotetrahydro-2H-pyran-3-yl 4-nitrobenzoate (Ip);
2-(Methoxy)-2-oxo-l-phenylethyl 4-nitrobenzoate (Iq);
2-Oxo-2 -phenylethyl benzoate (Ir);
2-Oxo-2-phenylethyl 3-methylbenzoate (Is);
2-Oxo-2-phenylethyl 4-bromobenzoate (It);
2-Oxo-2 -phenylethyl 4-chlorobenzoate (lu);
2-Oxo-2-phenylethyl nicotinate (Iv).
DETAILED DESCRIPTION OF THE INVENTION
Present invention provides a one step, one pot process for the synthesis of a-acyloxy carbonyl compounds with regio selectivity, wherein the starting material is an alkene.
The process leads to novel α-acyloxy carbonyl compounds that may be used as key structural motif for synthesis of useful, therapeutically active compounds.
The present invention provides a single-step, one pot process for the preparation of a- ac loxy carbonyl compounds of general formula (I)
Figure imgf000006_0001
GENERAL FORMULA I
wherein
R = H, alkyl, aryl or Bn; Rl = H, alkyl, aryl, -CH2OTBS, -CH2OBn, -OR or OMOM; Ar=aromatic or heteroaromatic;
comprising reacting alkene of formula (II), with an aldehyde of formula (III) ^' Ar-CHO
K. ■
(II) (ni) wherein, R, Rl, Ar are as defined above; in the presence of a NHC catalyst, a halogen source, triethyl amine and a solvent selected from di-methyl sulfoxide (DMSO) in air at temperature 15-30°C by stirring for 10-50 hours and isolating compounds of general formula (I) with >70% yields.
N-Heterocyclic carbene catalyst is selected from:
IVa IVb, IVc IVd IVe IVf
Figure imgf000007_0001
wherein, Vb is Ar = 2,4,6-(CH3)3C6H2; Vc is Ar = 2,6-iPr2C6H3.
Halogen source is selected from N-bromo succinamide (NBS), N-iodo succinamide (NIS) or N-chloro succinamide (NCS) and preferably NBS.
The above process for the preparation of a-acyloxy carbonyl compounds of formula (I), using IVa as NHC- catalyst is depicted below in Scheme 1. The present invention provides a process with variations of the NHC catalyst IVa-IVf yielding the corresponding a-acyloxy carbonyl starting from styrene and -N02-benzaldehyde as shown in Table 1.
Table 1- NHC catalyzed oxidative functionalization of styrene with 4-N02-benzaldehyde:
Optimization studies
Figure imgf000007_0002
9 IVa Cs2C03 DMSO 24
10 IVa KOBu' DMSO 16
1 1 IVa Et3N DMSO (5 eq) +THF 15 a: Reaction conditions: styrene (5 mmol), jp-nitrobenzaldehyde (6 mmol), NHC precatalyst (Va- f) (10 mol%), Base (6 mmol), NBS (5 mmol); all under 02 atmosphere in DMSO, 25°C, 18 h; b: isolated yield after column chromatographic purification; c: NIS is used instead of NBS; d: NCS is used us halogen source.
The present invention provides a process for the preparation of a-acyloxy carbonyl compounds of formula (II), wherein the NHC catalysts is preferably IVa to IVd with yields greater than 50%.
The present invention provides a process with options of aldehydes to provide a- acyloxy carbonyl with high regioselectivity yield greater than 70% as shown in Table 2.
Table 2: NHC catalyzed oxidative functionalization of styrene with aromatic aldehyde
Figure imgf000008_0001
a: Reaction conditions: styrene (5 m.mol), aromaticaldehyde (5.5 mmol), NHC precatalyst Va (10 mol%), Et3N (5.5 mmol), NBS (5 mmol) in DMSO under 02 atmosphere; 25°C; b:iso!ated yield after column chromatographic purification.
The present invention provides various a-acyloxy carbonyls synthesized by varying the alkenes (III), with >70% yield as shown in Table 3.
Table 3: NHC catalyzed oxidative functionalization of alkenes with 4-NC>2-benzaldehyde1 entry alkenes time products yield (%)"
(Ila-q) (n) (Ia-q)
1 styrene (Ila) 18 la 92
2 4-CH3-styrene (lib) 20 lb 77
3 4-Br- styrene (lie) 18 Ic 71
4 4-F- styrene (lid) 22 . Id 79
5 4-0 Ac- styrene (He) 23 Ie 82
6 3,4 -(OMe)2 styrene (Ilf) 26 If 74
7 indene (Ilg) 18 Ii 72
8 stilbene (Ilh) 24 Ij 81
9 Ph-CH=CH-CH2-OTBS (Hi) 28 Ig 92
10 3,4 -(0-CH2-0)-Ph-CH=CH 26 Ih 81
-CH2-OTBS (Ilj)
11 benzyloxy 1-propene (Ilk) 27 Ik 79
12 1-octene (III) 32 11 71
13 1 -decene (Ilm) 29 Im 76
14 4-phenyl-l-butene (Hn) 26 In 74
15 ethoxyethene (IIo) 30 Io 78c
16 dihydropyran (Hp) 28 ip 69
17 Ph-CH2-CH=CH-OCH2OCH3 (Ilq) 32 Iq 73 a: Reaction conditions: alkene (5 mmol), /?-nitrobenzaldehyde (5.5 mmol), NHC precatalyst IVa (10 mol%), Et3N (5.5 mmol), NBS (5 mmol) in DMSO under 02 atmosphere; 25°C; b:isolated yield after column chromatographic purification; c reaction was carried out at 0°C.
EXAMPLES
Following examples are given by way of illustration therefore should not be construed to limit the scope of the invention. :' EXAMPLE 1
GENERAL EXPERIMENTAL PROCEDURE
To a solution of alkenes (IIIa-q) (1 equiv.) in DMSO (20 ml), N-Heterocyclic carbene
(10 mol %), N-Bromo succinamide (1 equiv.), triethyl amine (1.2 equiv.) and aldehyde (IVa-f) were added under oxygen atmosphere. The reaction mixture was then stirred at 25°C. After completion (monitored by TLC), the reaction mixture was then concentrated, followed by the addition of H20 (50 mL). It was extracted with EtOAc (3 x 50 ml) and the combined organic layers dried over anhydrous Na2S04. Removal of solvent gave a-acyloxy carbonyls (Ia-v), which were purified by column chromatography over silica gel using pet ether/EtOAc (1/19) as eluent to obtain pure a-acyloxy carbonyls in high purity.
Example 2
2-Oxo-2-phenylethyl 4-nitrobenzoate (Ila):
Figure imgf000010_0001
Yield: 92%, colorless solid, Mp: 123-124 °C ; IR (Nujol, cm"1): 719, 1104, 1229, 1294, 1376, 1462, 1524, 1598, 1696, 1727, 275, 2840, 2923; Ή NMR (200 MHz, CDC13): δ 5.64 (s, 2H), 7.51 - 7.55 (m, 2H), 7.63 - 7.65 (m, 1H), 7.97 (d, J = 8.5 Hz, 2H), 8.33 (s, 4H); 13C NMR (50 MHz, CDC13) : δ 66.9, 123.4, 127.7, 128.9, 130.9, 133.8, 134.0, 134.7, 150.6, 164.0, 191.0: HRMS (ESI): [M+H]+ calcd for C 15HHN05+H: 286.0715; found: 286.0726.
2-(4-MethyIphenyl)-2-oxoethyl 4-nitrobenzoate (lib):
Figure imgf000010_0002
Yield: 77%, colorless solid, Mp: 1 14-1 15 °C; IR (Nujol, cm"1): 713, 1 135, 1231, 1289, 1374, 1459, 1525, 1604, 1692, 1725, 2840, 2923; Ή NMR (200 MHz, CDC13): δ 2.46 (s, 3H), 5.62 (s, 2H), 7.32 (d, J= 8.1 Hz, 2Ή), 7.87 (d, J= 8.1 Hz, 2H), 8.33 (s, 4H); ,3C NMR (50 MHz, CDCI3): δ 21.8, 66.9, 123.5, 127.8, 129.6, 131.1, 131.5, 134.8, 145.1, 150.7, 164.1, 190.6; HRMS (ESI): [M+H]+ calcd for: Ci6H13N05+H : 300.0872; found: 300.0881.
2-(4-Bromophenyl)-2-oxoethyl 4-nitrobenzoate (He):
Figure imgf000010_0003
Yield: 71%, colorless solid, Mp: 1 17-1 18 °C; IR (CHC13, cm"1): 717, 967, 1 106, 1 124, 1346, 1521, 1701, 1723, 2850, 2920; lH NMR (200 MHz, CDC13): δ 5.58 (s, 2H), 7.67 (m, J = 8.5 Hz, 2H), 7.83 (m, J= 8.5 Hz, 2H), 8.32 (s, 4H); ,3C NMR (100 MHz, CDC13) : δ 66.7, 123.6, 129.2, 129.5, 131.1, 132.4, 132.6, 134.6, 150.8, 164.0, 190.0; HRMS (ESI): [M+H]+ calcd for Ci5H10BrNNaO5+H: 363.9820; found: 363.9834.
2-(4-Fluorophenyl)-2-oxoethyl 4-nitrobenzoate (lid):
Figure imgf000011_0001
Yield: 79%, colorless solid, Mp:117-118 °C ; IR (CHC13, cm"1): 717, 871, 1131, 1155, 1231, 1320, 1521, 1595, 1698, 1722, 1746; 1H NMR (400 MHz, CDC13): δ 5.59 (s, 2H), 7.21 (t, J = 8.6 Hz, 2H), 8.01 (dd, J = 8.6, J = 5.0 Hz, 2H), 8.32 (d, J = 2.7 Hz, 4H); 13C NMR (100 MHz, CDC13): 6 66.7, 116.1, 116.4, 130.5, 130.5, 131.1, 134.6, 150.8, 164.0, 165.0, 167.5, 189.3; HRMS (ESI): [M+H]+ calcd for CI5H,oFN05+H: 304.0621; found: 304.0627.
2-(4-Acetoxyphenyl)-2-oxoethyl 4-nitrobenzoate (lie):
Figure imgf000011_0002
Yield: 82%, colorless solid, Mp: 128-129 °C; IR (Nujol, cm"1): 716, 1166, 1212, 1294, 1374, 1459, 1525, 1596, 1690, 1717, 1753, 2846, 2917; 1H NMR (200 MHz, CDC13): δ 2.35 (s, 3H), 5.61 (s, 2H), 7.26 (d, J= 8.6 Hz, 2H), 8.01 (d, J= 8.6 Hz, 2H), 8.32 (s, 4H); I3C NMR (100 MHz, CDC13): 5 21.0, 66.7, 122.2, 123.5, 129.3, 131.0, 131.3, 134.6, 150.6, 155.0, 164.0, 168.4, 189.9; HRMS (ESI): [M+H]+ calcd for C17H,3N07+H: 344.0770; found: 344.0778.
2-(3, 4 Dimethoxyphenyl)-2-oxoethyl 4-nitrobenzoate (Ilf):
Figure imgf000011_0003
Yield: 74%, colorless solid, Mp: 162-163 °C; IR (Nujol, cm"1): 720, 1021, 1131, 1255, 1376, 1460, 1524, 1684, 1725, 2855, 2925; Ή NMR (200 MHz, CDC13): δ 3.95 (s, 3H), 3.98 (s, 3H), 5.60 (s, 2H), 6.92 (d, J = 8.3 Hz, 1H), 7.51 - 7.54 (m, 2H), 8.33 (s, 4H); 13C NMR (100 MHz, CDCI3): δ 55.9, 56.0, 66.6, 110.0, 110.1, 122.1, 123.6, 127.1, 131.0, 134.9, 149.5, 150.8, 154.1, 164.1, 189.5; HRMS (ESI): [M+H] calcd for C17H,5N07+H: 346.0922; found: 346.0927. l-Oxo-2, 3-dihydro-lH-inden-2-yl 4-nitrobenzoate (Ilg):
Figure imgf000011_0004
Yield: 72%, colorless solid, Mp: 199-200 °C ; IR ( ujol, cm"1): 713, 1122, 1273, 1349, 1374, 1522, 1604, 1709, 1722, 2846, 2923; Ή NMR (200 MHz, CDC13): δ 3.23 (dd, J = 17.0, 4.9 Hz, 1H), 3.82 (dd, J= 17.0, 8.1 Hz, 1H), 5.70 (dd, J= 8.1, 4.9 Hz, 1H), 7.44 - 7.53 (m, 2H), 7.68 (d, J= 7.7 Hz, 1H), 7.86 (d, J= 7.7 Hz, 1H), 8.30 (s, 4H); 13C NMR (125 MHz, CDC13): δ 33.4, 75.0, 123.6, 124.7, 126.7, 128.4, 131.1, 134.5, 134.7, 136.1, 150.1, 150.9, 164.1, 199.3; HRMS (ESI): [M+H]+ calcd for: C16H,2N05+H: 298.0715; found: 298.0720.
2-Oxo-l,2-diphenylethyl 4-nitrobenzoate (Hh):
Figure imgf000012_0001
Yield: 81%, colorless solid, Mp: 1 14-1 15 °C; IR (Nujol, cm"1): 762, 1097, 1288, 1341, 1374, 1462, 1522, 1692, 1720, 2851, 2923; Ή NMR (200 MHz, CDC13): δ 7.13 (s, 1H), 7.41 - 7.58 (m, 8H), 7.99 (d, J= 7.2 Hz, 2H), 8.28 (s, 4H); 13C NMR (50 MHz, CDC13): δ 78.7, 123.5, 128.7, 128.8, 129.3, 129.7, 131.1, 133.2, 133.6, 134.4, 134.8, 150.7, 164.0, 192.6: HRMS (ESI): [M+Na]+ calcd for: C2,H,5N05+Na: 384.0848; found: 384.0853. l-Oxo-l-phenyIpropan-2-yl 4-nitrobenzoate (Hi):
Figure imgf000012_0002
Yield: 81%, colorless solid, Mp: 1 19-120°C; IR (Nujol, cm"1): 721, 965, 1122, 1270, 1374, 1462, 1522, 1599, 1692, 1725, 2851, 2923; Ή NMR (200 MHz, CDC13): δ 1.72 (d, J = 6.9 Hz, 3H), 6.23 (q, J = 6.9 Hz, 1H), 7.52 - 7.63 (m, 3H), 7.97 - 8.01 (m, 2H), 8.29 - 8.30(m, 4H) ; 13C NMR (100 MHz, CDCI3); δ 17.2, 72.6, 123.4, 128.4, 128.8, 130.9, 133.7, 134.8, 150.6, 163.9, 195.5; HRMS (ESI): [M+H]+ calcd for: Ci6H13N05+H :300.0872; found: 300.0877.
3-((Tert-butyldimethylsilyI)oxy)-l-oxo-l-phenylpropan-2-yI 4-nitro benzoate (Ilj):
Figure imgf000012_0003
Yield: 92%, colorless solid, Mp: 77-78 °C; IR (Nujol, cm"1): 718, 839, 1270, 1371, 1459, 1530, 1695, 1733, 2851, 2917; Ή NMR(200 MHz, CDC13): δ 0.00 (s, 3H), 0.02 (s, 3H), 0.82 (s, 9H), 4.1 (d, J = 5.1 Hz, 2H), 6.25 (t, J = 5.1 Hz, 1H), 7.47 - 7.62 (m, 3H), 8.00 - 8.04 (m, 2H), 8.29 - 8.30 (m, 4H); l3C NMR (100 MHz, CDC13): δ -5.4, 18.1, 25.6, 29.7, 62.9, 77.3, 123.5, 128.5, 128.7, 131.0, 133.7, 134.8, 135.2, 150.7, 163.9, 194.4; HRMS (ESI): [M+H]+ calcd for: C22H27N06Si+H: 430.1686; found: 430.1689.
3-(Benzyloxy)-2-oxopropyI 4-nitrobenzoate (Ilk):
Figure imgf000013_0001
Yield: 79%, colorless solid, Mp: 83-84 °C; IR (Nujol, cm"1): 718, 1083, 1283, 1374, 1459, 1517, 1722, 1739, 2851, 2823; Ή NMR (200 MHz, CDC13): δ 4.21 (s, 2H), 4.64 (s, 2H), 5.23 (s, 2H), 7.37 (s, 5H), 8.28 (d, J = 4.3 Hz, 4H); 13C NMR (125 MHz, CDC13): δ 67.8, 73.8, 73.9, 123.5, 127.9, 128.3, 128.6, 130.9, 134.6, 136.5, 150.7, 163.8, 200.8; HRMS (ESI): [M+Na]+ calcd for C17H,5N06+Na: 352.0796; found: 352.0801.
2-OxooctyI 4-nitrobenzoate (III):
Figure imgf000013_0002
Yield: 71%, colorless solid, Mp: 75-76 °C: IR (Nujol, cm"1): 717, 1121, 1272, 1352, 1377, 1463, 1536, 1543, 1722, 1733, 2854, 2923; lH NMR (200 MHz, CDC13): δ 0.87 - 0.93 (m, 3H), 1.26 - 1.31 (br. s, 6H), 1.67 - 1.70 (m, 2H), 2.49 (t, J- 7.3 Hz, 2H), 4.94 (s, 2H), 8.24 - 8.35 (m, 4H); l3C NMR (125 MHz, CDC13): δ 13.9, 22.4, 23.2, 28.7, 31.5, 38.7, 68.7, 123.5, 130.9, 134.6, 150.7, 163.8, 202.4: HRMS (ESI): [M+H]+ calcd for C|5Hi9N05+H: 294.1341; found: 294.1347.
2-Oxodecyl 4-nitrobenzoate (Ilm):
Figure imgf000013_0003
Yield: 76%, colorless solid, Mp: 76-77 °C; IR (Nujol, cm"1): 713, 11 19, 1270, 1374, 1459, 1541, 1610, 1717, 1736, 2857, 2928; Ή NMR (200 MHz, CDC13): δ 0.85 - 0.92 (m, 3H), 1.29 (br. s., 10H), 1.66 (t, J= 7.2 Hz, 2H), 2.49 (t, J= 7.2 Hz, 2H), 4.94 (s, 2H), 8.24 - 8.35 (m, 4H); 13C NMR (50 MHz, CDC13): δ 14.0, 22.5, 23.2, 29.0, 29.0, 29.2, 31.7, 38.6, 68.6, 123.4, 130.8, 134.6, 150.6, 163.7, 202.2; HRMS (ESI): [M+H]+ calcd for Ci7H23N05+H: 322.1654; found: 322.1656.
2-Oxo-4-phenyIbutyl 4-nitrobenzoate (Iln):
Figure imgf000014_0001
Yield: 74%, colorless solid, Mp: 112-113 °C; IR (Nujol, cm"1): 724, 1089, 1131, 1273, 1347, 1377, 1462, 1523, 1600, 1718, 1732, 2855, 2926; 1H NMR (200 MHz, CDC13) : δ 2.79 - 2.87 (m, 2H), 2.95 - 3.03 (m, 2H), 4.91 (s, 2H), 7.21 - 7.31 (m, 5H), 8.27 - 8.34 (m, 4H); 13C NMR (50 MHz, CDC13): δ 29.2, 40.4, 68.8, 123.6, 126.4, 128.2, 128.6, 131.0, 138.0, 140.2, 150.8, 163.9, 201.7; HRMS (ESI): [M+Na]+ calcd for: C.7H,5N05+Na: 336.0848; found:
Figure imgf000014_0002
Yield: 78%, yellow liquid; IR (neat, cm"1): 2926, 2983, 1759, 1738, 1732, 1608, 1531, 1349, 1285, 1213, 1121, 1018, 857, 718; 1H NMR (200 MHz, CDC13): δ 1.33 (t, J = 7.1 Hz, 3H), 4.28 (q, J = 7.1 Hz, 2H), 4.89 (s, 2H), 8.25 - 8.36 (m, 4H); 13C NMR (50 MHz, CDC13): δ 14.1, 61.5, 123.5, 131.0, 134.5, 150.8, 163.9, 166.9; HRMS (ESI): [M+Na]+ calcd for Ci ,H, iN06+Na: 276.0484; found: 276.0446.
2-Oxotetrahydro-2H-pyran-3-yl 4-nitrobenzoate (Hp):
Figure imgf000014_0003
Yield: 69%, colorless solid, Mp: 136-137 °C; IR (Nujol, cm"1): 718, 1 124, 1273, 1377, 1456, 1511, 1602, 1725, 1753, 2857, 2912; 1H NMR (200 MHz, CDC13): δ 2.14 - 2.20 (m, 3H), 2.51 - 2.76 (m, 1H), 4.43 - 4.49 (m, 2H), 5.61 - 5.67 (m, 1H), 8.25 - 8.35 (m, 4H); C NMR (50 MHz, CDC13): δ 21.3, 24.8, 68.2, 68.2, 123.5, 131.0, 134.5, 150.7, 163.4, 168.1; HRMS (ESI): [M+H]+ calcd for ¾ΗηΝ06+Η: 266.0664; found: 266.0663
2-(Methoxy)-2-oxo-l-pheny!ethyI 4-nitrobenzoate (Ilq):
Figure imgf000015_0001
Yield: 72%, yellow liquid; IR (CHC13, cm"1): 718, 1101, 1167, 1269, 1346, 1368, 1508, 1527, 1606, 1731, 1760; Ή NMR; (500 MHz, CDC13): δ 3.80 (s, 3H), 6.20 (s, 1H), 7.47 - 7.48 (m, 3H), 7.59 - 7.60 (m, 2H), 8.32 (s, 4H); l3C NMR (125 MHz, CDCI3): δ 52.6, 75.4, 123.5, 127.7, 128.9, 129.5, 131.0, 133.3, 134.5, 150.8, 163.7, 168.5; HRMS (ESI): [M+Naf calcd for Ci6Hi3N06+Na: 338.0641; found: 338.0649.
2-Oxo-2-phenylethyl benzoate (Ilr):
Figure imgf000015_0002
Yield: 68%, colorless solid, Mp: 119-120 °C ; IR (Nujol, cm"1): 705, 1015, 1374, 1459, 1596, 1714, 1750, 2851, 2923; Ή NMR (200 MHz, CDC13): δ 5.58 (s, 2H), 7.48 - 7.61 (m, 6H), 7.97 - 8.00 (m, 2H), 8.13 - 8.17 (m, 2H); 13C NMR (50 MHz, CDC13): δ 66.2, 127.6, 128.2, 128.73 , 129.8, 130.1, 133.1, 133.6, 134.1, 165.7, 191.6; HRMS (ESI): [M+Na]+ calcd for Ci5H1203+Na: 263.0683; found: 263.0692.
2-Oxo-2-phenylethyl 3-methylbenzoate (lis):
Yield: 81%, colorless solid, Mp: 94-95°C; IR
Figure imgf000015_0003
1 198, 1369, 1451, 1585, 1684, 1714, 2857, 2917; 'H NMR (200 MHz, CDC13): δ 2.38 (s, 3H), 5.52 (s, 2H), 7.31 - 7.48 (m, 5H), 7.90 - 7.95 (m, 4H); 13C NMR (100 MHz, CDC13): δ 21.1, 66.2, 127.0, 127.6, 128.2 128.7, 129.2, 130.3, 133.6, 133.9, 134.1, 137.9, 165.8, 191.7; HRMS (ESI): [M+Na]+ calcd for Ci6Hi403+Na: 277.0840; found: 277.0848. 2-Oxo-2-phenylethyl 4-bromobenzoate (lit) :
Figure imgf000016_0001
Yield: 78%, colorless solid, Mp: 84-85°C; IR (Nujol, cm"'): 766, 1012, 1126, 1327, 1588, 1643,1711, 1732, 2923, 2956; lH NMR (200 MHz, CDC13): δ 5.57 (s, 2H), 7.44 - 7.64 (m, 5H), 7.94 - 8.03 (m, 4 H); ,3C NMR (50 MHz, CDC13): δ 66.4, 127.7, 128.3, 128.4, 128.8, 131.4, 131.7, 133.8, 134.1, 165.0, 191.4: HRMS (ESI): [M+Na]+ calcd for Ci5HnBr03+Na: 340.9789; found: 340.9799. 2-Oxo-2-phenylethyl 4-chlorobenzoate (IIu):
Figure imgf000016_0002
Yield: 75%, colorless solid, Mp: 127-128 °C ; IR (Nujol, cm'1): 753, 1091, 1226, 1273, 1376, 1456, 1595, 1697, 1726, 2724, 2857, 2926; Ή NMR (500 MHz, CDC13): δ 5.58 (s, 2H) 7.44- 7.56 (m, 5H), 7.97(d, J= 7.3 Hz, 2H) 8.07 - 8.11 (d, J= 7.3 Hz, 2H); 13C NMR (125 MHz, CDC13): δ 66.5, 77,0, 127.8, 128.6, 128.8, 128.9, 131.3, 133.9, 134.2, 139.8, 165.0, 191.6; HRMS (ESI): [M+Na]+ calcd for Ci5H, ,C103+Na: 297.0294; found: 297.0294.
2-Oxo-2-phenylethyl riicotinate (IIv)
Figure imgf000016_0003
Yield: 73%, colorless solid, Mp: 64-65 °C: IR (CHC13, cm"): 753, 1076, 1342, 1463, 1591, 1650, 1695, 1726, 2854, 2870, 2923; Ή NMR (400 MHz, CDC13); δ 5.61 (s, 2H), 7.44 (dd, J= 7.6, 4.9 Hz, 1H) 7.50 - 7.54 (m, 2H), 7.62 - 7.64 (m, 1H), 7.97 (d, J= 7.5 Hz, 2H), 8.40 (d, J= 7.7 Hz, 1H), 8.82 (br. s, 1»), 9.33 (br. s, 1H); 13C NMR (100 MHz, CDC13) δ 66.6, 123.3, 125.6, 127.8, 128.9, 134.0, 134.1, 137.4, 151.2, 153.7, 164.6, 191.1; HRMS (ESI): [M+Na]+ calcd for C14H, ,N03+Na: 264.0637; found: 264.0648.
ADVANTAGES OF THE INVENTION
A new catalytic regio selective method for the preparation of acyloxy carbonyl products in preparative yield from a variety of olefins including aromatic, aliphatic and electron rich at ambient conditions is disclosed. Tjhis method is simple, milder and the reagents used are cheap and easy to handle. The process avoids metal catalysts.

Claims

A single-step, one pot process for preparation of a-acyloxy carbonyl compound of general formula (I)
Figure imgf000018_0001
General formula (I)
wherein R is selected from H, alkyl, aryl, Bn; R1 is selected from H, alkyl, substituted aryl, unsubstituted aryl -CH2OTBS (TBS=Tertiary butyl silyl), -CH2OBn, -OR, OMOM (Methoxy methelene); Ar is selected from substituted aromatic, unsubstituted aromatic or heteroaromatic; R and Rl optionally can combine to form a ring structure;
comprising the steps of:
i) reacting alkene of formula (III) with an aldehyde of formula (IV)
_ ^¾^ Ar-CHO
R ^
(II) (III)
in the presence of a N-Heterocyclic carbene catalyst (NHC), a halogen source, tri-ethyl amine and a solvent in oxygen atmosphere at a temperature in the range of 15-30°C by stirring for period in the range of 10-50 hours to obtain compound of general formula (I); wherein R is selected from H, alkyl, aryl, Bn; R1 is selected from H, alkyl, substituted aryl, unsubstituted aryl -CH2OTBS (TBS=Tertiary butyl silyl), -CH2OBn, -OR, OMOM (Methoxy methelene); Ar is selected from substituted aromatic, unsubstituted aromatic or heteroaromatic.
The process as claimed in claim 1, wherein N-Heterocyclic carbene catalyst is selected from the group consisting of IVa-I Vf, preferably IVa.
IVa IVb. IVc IVd IVe IVf
Figure imgf000018_0002
Wherein for IVb, Ar = 2,4,6-(C¾)3C6H2; for IVc, Ar = 2,6-iPr2C6H3
3. The process as claimed i claim 1, wherein halogen source is selected from the group consisting of N-bromo succinamide (NBS), N-iodo succinamide NIS or N-chloro succinamide NCS, preferably NBS.
4. The process as claimed in claim 1, wherein solvent used is di-methyl sulfoxide (DMSO). 5. The process as claimed in claim 1 , wherein yield of the compound of general formula 1 is in the range of 70 to 92%.
6. The process according to claim 1, wherein representative compound of general formula I are:
2-Oxo-2-phenylethyl 4-nitrobenzoate (la);
2-(4-Methylphenyl)-2-oxoethyl 4-nitrobenzoate (lb);
2-(4-Bromophenyl)-2-oxoethyl 4-nitrobenzoate (Ic);
2-(4-Fluorophenyl)-2-oxoethyl 4-nitrobenzoate (Id);
2-(4-Acetoxyphenyl)-2-oxoethyl 4-nitrobenzoate (Ie);
2-(3, 4 Dimethoxyphenyl)-2-oxoethyl 4-nitrobenzoate (If);
1- Oxo-2, 3-dihydro-lH-inden-2-yl 4-nitrobenzoate (Ig);
2- Oxo-l,2-diphenylethyl 4-nitrobenzoate (Ih);
1- Oxo-l-phenylpropan-2-yl 4-nitrobenzoate (Ii);
3- ((Tert-butyldimethylsilyl)oxy)-l-oxo-l-phenylpropan-2-yl 4-nitro benzoate (Ij);
3-(Benzyloxy)-2-oxopropyl 4-nitrobenzoate (Ik);
2- Oxooctyl 4-nitrobenzoate (II);
2-Oxodecyl 4-nitrobenzoate (Im);
2-Oxo-4-phenylbutyl 4-nitrobenzoate (In);
2-Ethoxy-2-oxoethyl 4-nitrobenzoate (Io);
2-Oxotetrahydro-2H-pyran-3-yl 4-nitrobenzoate (Ip);
2-(Methoxy)-2-oxo-l-phenylethyl 4-nitrobenzoate (Iq);
2-Oxo-2-phenylethyl benzoate (Ir);
2-Oxo-2-phenylethyl 3-methylbenzoate (Is);
2-Oxo-2-phenylethyl 4-bromobenzoate (It);
2-Oxo-2-phenylethyl 4-chIorobenzoate (Iu);
2-Oxo-2 -phenylethyl nicotinate (Iv).
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