Self and cross-metathesis of allylisothiocyanate with alkyl esters by grubbs 2nd generation catalyst

Abstract

Allylisothiocyanateundergoes self-metathesis by 2nd generation Grubbs catalyst to give 1,4-
disothiocyanatobut-ene together with the release of styrene and phosphine ligands. Despite the release of both ligands cross metathesis with methyl oleate, ethyl oleate and ethyl linoleatestill gave some targeted cross and self-metathesis products.1-isothiocyanatoundec-2-ene was detected in all the cross-metathesis reaction. Methyl11-isothiocyanatoundec-9-enoate and ethyl-11-isothiocyanatoundec-9-enoateare
products of another cross-metathesis with methyl oleate and ethyl oleate respectively. Under the
reaction conditionno other cross product with ethyl linoleate was detectedexcept the formation of side
products ofcarbene species possibly due to side reactions such as isomerization and addition. The
formation of 1-isothiocyanatomethylstyreneis the result of the cross metathesis between
allylisothiocyanate and styrene. The study indicated that the sulfur atom is more sensitive than oxygen
atom to interact with the catalyst resulting in the release of the phosphine and styrene from catalytic
cycle. Therefore a suitable protecting agent is necessary to sustain the catalytic cycle.