DE1112731B - Process for the preparation of 2-methylhepten- (2) one- (6) - Google Patents

Description

The present invention relates to a new process for the preparation of 2-methylhepten- (2) one- (6).

It has been found that 2-methylhepten- (2) one- (6) can be prepared on an industrial scale if acetone or diacetone alcohol, l-chloro-3-methylbutene- (2) and an alkaline condensing agent, namely sodium or Potassium hydroxide, mixed together using for each mole of 1-chloro-3-methylbutene- (2) about 1 to 5 moles of acetone and about Vi to 3 moles of alkaline condensing agent, then the mixture for about Va to 8 hours at about 0 to 80 ⁰ C is stirred and the 2-methylhepten- (2) one- (6) formed is isolated.

2-Methylhepten- (2) one- (6) - hereinafter referred to as methylheptenone for short - is an important intermediate for synthesis. One has long been following its technical synthesis from easily accessible substances sought. The present process according to the invention gives satisfactory yields of industrially useful Methylheptenone from simple and inexpensive raw materials.

For the production of 1-chloro-3-methylbutene- (2), isoprene is used in a manner not claimed here with concentrated hydrochloric acid with vigorous stirring. There is separation in two layers. The organic Layer is dried and then for the purpose of obtaining the l-chloro-3-methyl-butene- (2) fractionally distilled.

Acetone and l-chloro-3-methylbutene- (2) can be made using sodium hydroxide or potassium hydroxide condensed well together to give methylheptenone. It is surprising that you are with Potassium hydroxide achieves a yield of 40 to 50% of methylheptenone, while with sodium hydroxide only yields of about 20 to 30% can be obtained. Because of the higher base strength of the potassium hydroxide it was to be assumed that more side reactions would occur, for example the basic one catalyzed self-condensation of acetone or the condensation of the ketone residues obtained as the end product Methylheptenone. However, it has been found that potassium hydroxide is particularly effective in achieving this high yields of methylheptenone and thus enables an industrial synthesis. The procedure below Using sodium hydroxide is also an industrially viable synthesis, even if it is only 20-bis 30% yield results.

When selecting the time and temperature at which acetone and 1-chloro-3-methylbutene- (2) are to be reacted with one another in the presence of the alkaline condensing agent, it must be remembered that, in addition to the desired course of the reaction, the process for preparation
of 2-methylhepten- (2) one- (6)

Applicant:

Societe des Usines
Chimiques Rhone-Poulenc, Paris

Representative: Dr. F. Zumstein,

Dipl.-Chem. Dr. rer. nat. E. Assmann

and DipL-Chem. Dr. R. Koenigsberger, patent attorneys,

Munich 2, Bräuhausstr. 4th

Claimed priority:
V. St. v. America January 3, 1958 (No. 706 888)

Hugh E. Ranisden, Scotch Plains, N.J.,

Edith H. Miller, Milltown, NJ,
and Ambrose J. Gibbons, South River, NJ

(V. St. A.),
have been named as inventors

Side reactions can also take place in the formation of methylheptenone. For example, high temperatures and long process times cause self-condensation of the acetone or a condensation of acetone with already formed methylheptenone, which reduces the yields. Another side reaction is the further conversion of methylheptenone with 1-chloro-3-methylbutene- (2) to di-isopentenyl-acetone. Reaction times of 1 to 4 hours at 10 to 30 ^° C. are particularly suitable. Instead of acetone, diacetone alcohol, ie a base-catalyzed condensation product of acetone with 1-chloro-3-methylbutene- (2), can also be used as the end product for the preparation of methylheptenone. Such a procedure is given in Example 4 below. It is entirely possible that, during the usual condensation of acetone with 1-chloro-3-methylbutene- (2), the basic catalyst present permits the condensation of acetone to form diacetone alcohol during the reaction time. In

109 678/223

3 4

this case proceeds the formation of methylheptenone residue which was distilled to give the following

via a condensation reaction in which diacetone fractions:

alcohol occurs as a reactive intermediate. Group I: Kp _lo 30 to 5O ⁰ C, yield 5.6 g;.

The order of addition is not essential. _{FraktioQ n} . _{K 60 Ms 70} " _{c yield} 39.5 _&

Virtually every possible variation has been tried. 5 _es _ j 4350-

For example, an attempt was made to first add a °. ' _TTT ',. __ _o _,. _u,. "

Mixture of 1-chloro-3-methylbutene- (2) and acetone ^Fra k ^ü ™ HI: bp ₇ 66 to 70 ⁰ C, yield 14.8 g,

to potassium hydroxide, secondly the addition of acetone ⁿ ° ' '

to 1-chloro-3-methylbutene- (2) and potassium hydroxide, fraction IV: residue 27.9 g.

thirdly, the addition of 1-chloro-3-methylbutene- (2) to 10 Infrared analysis of fractions II and III showed

Acetone and Potassium Hydroxide and, fourthly, the rapid that it was methylheptenone. Yield:

Mix all three ingredients together. 43% methylheptenone.

All of these methods have been found to be effective. The same results were obtained when the

grasslands. Components all at the same time in the flask

The form in which the alkaline condensing agent 15 were given

is used is related to the yield. The example 2

Surface should be as large as possible to the greatest _TT ^ _t "

possible contact of the alkaline agent with those used to manufacture methylheptenone

to achieve condensing substances. Potassium hydroxide- ^from sodium hydroxide

flakes have therefore proven to be very suitable. 20 To 1 mole of sodium hydroxide, 100 ml of tetra-

In addition, an excess of potassium hydroxide hydrofuran is added. A mixture was added to this

used because its surface is coated and made from 1 mole of acetone and 1 mole of l-chloro-3-methylbutene

this limits the yield. (2) slowly in about 1 hour. During the encore

A small amount of tetrahydrofuran was added to the ratio of acetone to 1-chloro-3-methyl-.

butene (2) and the alkaline condensation agent 25 After the addition was complete, the reaction

affects the yield. Experimentally, the solid mixture was stirred at 65 ° C. for 4 hours. To the

made that good yields are obtained when a mixture was then given 100 ml of water and

Ratio of 3 moles of acetone to 1 mole of 1-chlorine- the separated organic layer was collected. the

3-methylbutene- (2) and 2 moles of potassium hydroxide with aqueous layer was twice with low-boiling

about 10 to 30 ⁰ C can be used. 30 washed petroleum ether and add the washing water to the

The l-chloro-3-methylbutene- (2) can be added in pure form to organic layers. The organic layer

be admitted. Preferably, however, the crude was dried and distilled and gave the following-

Form related, as it is not claimed here, to the two fractions:

Way from isoprene and concentrated hydrochloric acid- _{Fraction I: boiling point 40} to 45 ⁰ C, yield 18.8 g,

will hold. The raw form also contains some 3-chloro 35 ₂₅ _, 4440:

3-methylbutene- (l). In the condensation reaction -, ". ' _TT ^ - ™ ^ - « o ^ _A u * -1 1

part of the 3-chloro-3-methylbutene- (l) isomerized and fraction II: .Kp. ₆ 50 to 55 C, yield 7.1 g,

thus results in methylheptenone. With such a use of ⁿ ° ~~ l ^'44 ™ ·

of the crude material are higher yields. Fractions I and II were combined and

hold because the 3-chloro-3-methylbutene- (l) -Nebenpro- 40 distilled again and gave the fraction III.

duct is used. In addition, using p _rQ ir + ir.n τττ · T ^ r, * c \ ° r *, & - 1 A ^ ea
making the raw product more economical,

since the crude product is not fractionated to distill- Fractions I and II are crude methylheptenone,

need to lean. such as the formation of the 2,4-dinitrophenylhydrazone derivative

This is shown by the method according to the invention. The yield of fractions I and II was 20 ° / ₀ · possible, for 2-methylhepten- (2) one- (6) on one

much shorter and more economical way to get to Example 3
than that of Arens in Recueil des Travaux Chimiques

des Pays-Bas, 67: 977 (1948). Production of methylheptenone via diacetone

In the known process, acetoacetic ester is mixed with 50 alcohol.

Isoprenyl bromide implemented, which is much more complicated. To 1 mole of 1-chloro-3-methylbutene- (2) and 1 mole

Potassium hydroxide flakes were 1.38 moles of a diacetone alcohol prepared separately in 25 minutes

_TT . " _X , .v ,, ^ ,,. given. The reaction mixture was 3Va hours

Manufacture of methylheptenone using ^ ^ ^^ ^ ^ ^ ^^ ^, ^ ^

Kahumhydroxyd _given _ _{The gidi separating organic} layer

174 g (3 moles) of acetone were slowly collected into one and dried over sodium sulfate.

Mixture, which was stirred, was 104 g (1 mole). Then the organic layer was distilled to give

l-chloro-3-methylbutene- (2) and 112.0 g (2MoI) Ka- the following four fractions:
lium hydroxide flakes in about 1 hour with a 60 _{p ki χ K 3Q w} ^ _c yield 12.9 g,

Temperature of 20 ⁰ C added. The mixture "25 = 14430 ·

was stirred at 20 ° C. for a total of 4 hours. The ^D ''

Reaction mixture was then with 300 ecm of water fraction II: bp ₂₅ 50 to 60 C, yield 4.5 g,

hydrolyzed. Two layers formed. The "° ^S ~~ M430;

organic layer was collected and dried over Na ₂ SO ₄ 65 Fraction III: boiling point ₁₄ 61 to 65 ⁰ C, yield 27.0 g,

or K ₂ CO ₃ dried for about 30 to 45 minutes- «I ⁶ = 1> ⁴³⁸ 0;

net. The volatile components were obtained by distillation. Fraction IV: boiling point ₁₄ 65 to 66 ° C, yield 3.4 g,

removed, leaving 86 g of residue. The n% ³ = 1.4420.

Fraction III was obtained from the preparation of the 2,4-dinitrophenylhydrazone derivative and identified as methylheptenone by infrared analysis. The fraction III yield was 21%.

Example 4

A mixture of 6 mol of acetone, 2 mol of 1-chloro-3-methylbutene (2) and 4 mol of potassium hydroxide was added to a flask at 20 ° C and stirred for I ¹ J ₂ hours. 400 ml of water were added to the mixture. The organic layer which separated was collected and dried over potassium carbonate. It was then distilled and gave the following four fractions:

Fraction I: bp ₂₀ 28 ° C - bp ₁₆ 48 ° C, yield 46.8 g, 11 ^ = 1.4448;

. Group II: Kp _a 55 to 58 ° C, yield 31.4 g, '' S * = 1.4341;

Fraction III: bp ₆ 50 to 55 ° C, yield 59.7 g, "f = 1.4368;

Fraction IV: residue 38.2 g.

Fractions II and III are methylheptenone, which was obtained in 36% yield ^it is.

Methylheptenone is an important synthetic intermediate for the production of citral, citronellol and vitamin A. It is particularly useful as an intermediate in the synthesis of the perfume ingredient Linalool, for example by vinylating methylheptenone.

Claims (4)

PATENT CLAIMS: 1. A process for the preparation of 2-methylheptene - (2) one - (6), characterized in that acetone or diacetone alcohol, l-chloro-3-methylbutene- (2) and sodium or potassium hydroxide are reacted with one another as an alkaline condensing agent, where for each mole of l-chloro-3-methylbutene- (2) about 1 to 5 moles of acetone and ^χ / ₄ to 3 moles of alkaline condensing agent can be used by adding these ingredients approximately V2 to 8 hours at about 0 to 80 ° C intimately with one another stirred and the 2-methylhepten- (2) one- (6) formed was isolated. 2. The method according to claim 1, characterized in that a ratio of acetone to 1-chloro-3-methylbutene- (2) and applied to the alkaline condensing agent of about 3: 1: 2. 3. The method according to claim 1 and 2, characterized in that temperatures of approximately 10 to 30 ° C and reaction times of about 1 to 4 hours to be applied. 4. The method according to claim 1 and 2, characterized in that temperatures of about 60 to 80 ° C and reaction times of about ¹ J ₂ to I ¹ J ₂ hours are used. Considered publications:
Recueil des Trav. Chim. des Pays-Bas, Vol. 67, 1948, pp. 977 and 975. © 109 678/223 8.61