Process for the preparation of lineatin

Details Process for the preparation of lineatin Process for the preparation of lineatin

1984-11-15

1986-03-25

Love, Ethel G.

Organic compounds -- part of the class 532-570 series

Organic compounds

Heterocyclic carbon compounds containing a hetero ring...

C07D31904, C07D32304

Patent

active

045784841

DESCRIPTION:

BRIEF SUMMARY
It is known that lineatin is a pheromone which attracts certain species of ambrosia beetles (Trypodendron). This attraction is particularly strong when lineatin is used in admixture with certain other chemical substances, for instance as described in our Norwegian Pat. No. 144.029.
There are described several processes for the preparation of lineatin, and the following may be mentioned: Silverstein, R. M.; Slessor, K. N.; Swigar, A. A. and Wong, D. T. W. J. Chem. Ecol. 5 (1979) 681. Grewal, S. K. and Wickremesinghe, L. K. G. J. Org. Chem. 45 (1980) 2290 (1982) 872. (1982) 1921. (1982) 5486.
None of these known processes can be considered as satisfactory with respect to yield, economy and simple operation. Thus, several are carried out by using photochemical reactions, which may easily give rise to considerable problems, particularly when carried out in large scale.
According to the invention there has been found a new process which leads to the desired lineatin with satisfactory yield by using commercially available cheap reagents and solvents, without using photochemical reactions.
The process according to the invention may be illustrated as follows: ##STR2## R.sub.1 and R.sub.2 may be hydrogen or lower alkyl. The examples illustrate R.sub.1 .dbd.R.sub.2 .dbd.H (a) and R.sub.1 .dbd.R.sub.2 .dbd.CH.sub.3 (b).
The preparation of 1 may be carried out in a per se known manner (U.S. Pat. No. 3,236,869) by reacting isobutyraldehyde with propargylalcohol (R.sub.1 .dbd.R.sub.2 .dbd.H) or a suitable derivative thereof in the presence of a catalyst such as p-toluene sulfonic acid.


STEP i

The preparation of the new compound 2 suitably takes place in a per se known manner (Bly et al, J. Am. Chem. Soc. 91 (1969) 3292) by reacting 1 with a suitable Grignard reagent, such as .beta.-methyl allylmagnesium chloride.


STEP ii

The preparation of the new compound 3 also takes place in a per se known manner [Brown et al, J. Am. Chem. Soc. 83 (1961) 2952 and J. Org. Chem., 36 (1971) 387] by oxidizing 2 with a mild oxidizing agent which oxidizes the secondary hydroxyl group to a keto group without attacking the double bond in 2. Suitable oxidizing agents are for instance bichromate, Jones reagent and DMSO.


STEP iii

The preparation of the new compound 4 from 3 is an important feature of the invention.
Here the reaction is a thermal intramolecular cyclo-addition in which the reaction conditions are dependant upon several factors, including the groups R.sub.1 and R.sub.2. In order to attain complete reaction it is necessary that the compound 3 is kept for some time at a specific temperature. In practice the reaction may be carried out by distilling the compound through a suitably heated tube under reduced pressure. Too high temperatures, such as above 550.degree. C., may result in excessive amounts of other products such as 8 due to competing reactions, while too low temperatures, such as below 400.degree. C., will result in incomplete reaction. The lower the reaction temperature is, the longer the reaction time must be. The reaction time may for instance be adjusted by varying the pressure when the compound 3 is distilled through a heated tube, since higher pressure will result in a longer residence time in the reactor. Normally the pressure is kept lower than 10 mm Hg. It is also possible to extend the residence time (reaction time) by using a longer reactor and/or increase the resistance therein. When for instance R.sub.1 .dbd.R.sub.2 .dbd.H and the length and the diameter of the tube are 60 cm and 2.5 cm respectively, and it is packed with silica wool, the suitable temperature will be 470.degree.-510.degree. C., preferably 480.degree.-500.degree. C., in particular about 490.degree. C.


STEP iv

Compound 4 is converted to the new compound 5 by simultaneous ring expansion of the cyclopentane ring and oxidation of the double bond by means of a suitable oxidizing agent, particularly an organic peracid such as an optionally substituted perbenzoic acid or pertrifluoro acetic acid.


STEP v

Compound 5 is converted to compoun

REFERENCES:
patent: 4296036 (1981-10-01), Mori et al.

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