RU2322431C1 - 1,2,3,4-tetraalkyl-1-iodo-1,3-butadiene preparation method - Google Patents

Abstract

FIELD: organic synthesis.

SUBSTANCE: method comprises stirring 1,2-disubstituted acetylenes with n-BuMgCl in diethyl ether in presence of zirconacene dichloride under argon atmosphere at room temperature during 3 h, cooling reaction mass to 0°C and adding I-₂ ether solution, and stirring at 20°C for further 3-5 h.

EFFECT: increased selectivity of reaction without use of pyrophoric butyllithium.

1 tbl, 10 ex

Description

The present invention relates to organic chemistry, specifically to an improved method for producing 1,2,3,4-tetraalkyl-1-iodo-1,3-butadiene of the general formula (I):

Substituted 1-iodo-1,3-butadiene can find application in fine organic and organometallic synthesis as starting intermediates in the synthesis of substances with biological activity, as well as polymer compounds.

The known method ([1], T. Takahashi, W.-H. Sun, C. Xi, H. Ubayama and Z. Xi. Selective one carbon-carbon bond formation reaction of zirconacyclopentadienes with aryl iodides or alkynyl iodides // Tetrahedron, 54 (1998) 715-728) for the preparation of substituted 1-iodo-1,3-butadiene (2) by reacting bis-cyclopentadienyl zirconacyclopentadienes with phenyl iodide in the presence of 2 equiv. CuCl and 2.5 equiv. DMF at 50 ° C followed by treatment of the reaction mass with an ether solution of I ₂ according to the scheme:

In a known manner, 1,2,3,4-tetraalkyl-1-iodo-1,3-butadiene (1) cannot be obtained.

The known method ([2], SLBuchwald, RBNielsen. Selective, zirconium-mediated cross-coupling of alkynes: the synthesis of isomerically pure 1,3-dienes and 1,4-diiodo-1,3-dienes // J. Am. Chem. Soc., 111 (1989), 2870-2874) for the preparation of substituted 1-iodo-1,3-butadiene (1) by the interaction of tetrasubstituted bis-cyclopentadienyl zirconacyclopentadienes obtained by the interaction of 1,2-disubstituted acetylenes with a stoichiometric amount of zirconocentinedichloride (Cp ₂ ZrCl ₂ ), pretreated with two equivalents of butyl lithium (n-BuLi) at -78 ° C in tetrahydrofuran, followed by the addition of I ₂ at a temperature of -78 ° C according to the scheme:

The known method for producing 1,2,3,4-tetraalkyl-1-iodo-1,3-butadiene (1) involves the use of a stoichiometric amount of expensive zirconacenedichloride (Cp ₂ ZrCl ₂ ), pyrophoric n-BuLi, in addition, during the reaction it is necessary maintain a low temperature of -78 ° C.

An improved method for the synthesis of 1,2,3,4-tetraalkyl-1-iodo-1,3-butadiene (1) is proposed.

The essence of the method consists in the interaction of disubstituted acetylenes of the formula R-≡-R, where R = C ₂ H ₅ , n-C ₃ H ₇ , n-C ₄ H ₉ , with n-BuMgCl in the presence of Cp ₂ ZrCl ₂ zirconacenedichloride catalyst taken in a molar ratio of R-≡-R: n-BuMgCl: Cp ₂ ZrCl ₂ = 10: (22-26) :( 1.0-1.4), preferably 10: 24: 1.2, stirring for 3 hours and then adding at 0 ° C of an ethereal solution of I ₂ in an amount of 1.1 molar equivalents with respect to n-BuMgCl and stirring the reaction mixture in an argon atmosphere at room temperature (~ 20 ° C) and atmospheric pressure for 3-5 hours. The yield of target products is 45-59%. It is necessary to use diethyl ether as a solvent; in other ethereal solvents (THF, dioxane), the yield of the target products (1) is significantly reduced.

The reaction proceeds according to the scheme:

The target products (1) are formed only with the participation of disubstituted acetylenes, n-BuMgCl, I ₂ and the catalyst Cp ₂ ZrCl ₂ . In the presence of other catalysts based on transition metal complexes (for example, Zr (acac) ₄ , Cp ₂ TiCl ₂ , Pd (acac) ₂ , Ni (acac) ₂ , Fe (acac) ₃ ), the target products (1) are not formed.

The reaction in the presence of a catalyst Cp ₂ ZrCl ₂ more than 14 mol.% With respect to acetylene does not lead to a significant increase in the yield of the target products (1). The use of Cp ₂ ZrCl ₂ in the reaction of the catalyst less than 10 mol.% Reduces the yield of MOS (1), which is associated with a decrease in catalytically active centers in the reaction mass. The experiments were carried out at room temperature ~ 20 ° C. At a higher temperature (for example, 50 ° C), the content of compaction products increases, at a lower temperature (for example, 0 ° C) the reaction rate decreases.

A change in the ratio of the starting reagents in the direction of increasing the content of n-BuMgCl with respect to acetylene does not lead to a significant increase in the yield of the target products (1). A decrease in the amount of n-BuMgCl with respect to acetylene reduces the yield (1).

Significant differences of the proposed method:

1. In the proposed method, n-BuMgCl and catalytic amounts of Cp ₂ ZrCl ₂ are used as a starting reagent. In the known method, 1-iodo-1,3-butadiene (1) is obtained from a stoichiometric amount of Cp ₂ ZrCl ₂ and a pyrophoric butyllithium reagent with an additional reduction step of Cp ₂ ZrCl _{2 with} butyl lithium.

The proposed method has the following advantages:

1. The method allows to obtain with high selectivity 1,2,3,4-tetraalkyl-1-iodo-1,3-butadiene (1) using catalytic amounts of expensive zirconacenedichloride without the use of pyrophoric n-BuLi.

The method is illustrated by the following examples:

EXAMPLE 1. In a 50 ml glass reactor mounted on a magnetic stirrer, 1.2 mmol of Cp ₂ ZrCl ₂ , 10 mmol of oct-4-in, and 24 mmol of n-BuMgCl (2M solution in Et ₂ O). Stirred at room temperature for 3 hours. Next, the reaction mass is cooled to 0 ° C and 26.4 mmol 12 (ether solution) is added dropwise. The temperature was brought to room temperature and stirred for 4 hours. An individual 4-iodo-5,6-dipropyl-4,6-decadiene (3) is obtained with a yield of 52%.

Spectral characteristics of 4-iodo-5,6-dipropyl-4,6-decadiene (3).

¹³ C NMR spectrum (δ, ppm): 13.57 (C ^13.16 ), 14.0 (C ¹⁰ ), 14.44 (C ¹ ), 21.97 (C ¹⁵ ), 22.45 (C ² ), 22.51 (C ¹² ) , 23.58 (С ⁹ ), 31.78 (С ¹¹ ), 32.33 (С ⁸ ), 33.81 (С ¹⁴ ), 54.75 (С ³ ), 117.24 (С ⁴ ), 132.52 (С ⁷ ), 152.3 (С ⁵ ), 154.48 (C ⁶ ).

Other examples confirming the method are shown in table 1.

Table 1 №№ R-≡-R The molar ratio of RC = CR: n-BuMgCl: I ₂ : Cp2ZrCl ₂ , mmol Reaction time, hour Yield (1),% one hex-3-in 10: 24: 26.4: 1.2 7 55 2 " 10: 26: 28.6: 1.2 7 57 3 " 10: 22: 24.2: 1.2 7 fifty four " 10: 24: 26.4: 1.4 7 59 5 " 10: 24: 26.4: 1.0 7 45 6 " 10: 24: 26.4: 1.2 8 54 7 " 10: 24: 26.4: 1.2 6 48 8 oct-4-in 10: 24: 26.4: 1.2 7 52 9 dec-5-in 10: 24: 26.4: 1.2 7 47

All experiments were carried out at room temperature (~ 20 ° C) in diethyl ether.

Claims (1)

The method of producing 1,2,3,4-tetraalkyl-1-iodo-1,3-butadiene of the general formula (I)

, where R = C ₂ H ₅ , n-C ₃ H ₇ , n-C ₄ H ₉ comprising the interaction of 1,2-disubstituted acetylenes with an organometallic compound in the presence of a zirconacene dichloride catalyst (Cp ₂ ZrCl ₂ ) in a solvent medium, followed by the addition of I ₂ characterized in that as the organometallic compound, n-BuMgCl is used at a molar ratio R-≡-R: n-BuMgCl: Cp ₂ ZrCl ₂ = 10: (22-26): (1.0-1.4), reaction carried out in diethyl ether at 20 ° C, and the subsequent addition of an ether solution of I ₂ at 0 ° C with further stirring in argon at 20 ° C for 3-5 hours