Thioureas reaction with acetylenic esters

The reaction of thiourea with acetylenic esters has been variously reported to give a thiazolin-4-one (372), an imidazolinethione (373), or a l,3-thiazin-4-one (374) " derivative. However, recent studies have shown that in fact it is the thiazolin-4-one (372) that is formed in this reaction [Eq. (55)]. In the light of this observation, it may now be necessary to revise the structures of products obtained from the reaction of A -methylthiourea, M -dimethylthiourea, and thiosemicarbazides with acetylenic esters. The reaction of a thiourea derivative such as A(-thiocarbamoylpiperidine with DMAD is reported to give 5-(carbomethoxymethylene)-2-piperidino-A -1,3-thiazolin-4-one (375) [Eq. (56)]. °... 

A simple procedure leading to methyl 2,5-dienoates utilizes allyl halides, acetylene, CO, and CH3OH. The reaction occurs at room temperature and atmospheric pressure and is based upon in situ formation of a catalytic complex of Ni with thiourea. The products contain a cis-double bond conjugated with the ester group. 

---