Allylic derivatives thiocarbonylation

Some applications of the thio-Claisen rearrangement to the syntheses of thiocarbonyl compounds, particularly unsaturated dithiocstcrs and thionesters, and of its stereocontrol aspects are reviewed in [120]. A particularly high stereoselectivity was observed with S-allyl derivatives of P-hydroxydithioesters syn products were obtained exclusively, according to the accompanying scheme [495,496]. 

The modification of cellulose with alkaline carbon disulfide to introduce xanthate groups has been extensively exploited in the industrial production of viscose. Early work on the preparation and properties of starch xanthate has been discussed. Xanthate derivatives of cellulose and starch have been discussed with respect to general xanthate chemistry, and the xanthation of cellulose in homogeneous medium is known to be a second-order reaction. Cellulose xanthate shows some potential as a matrix for enzyme insolubilization, " and stable derivatives of this xanthate may be prepared by transesterification. Thermal decomposition of cellulose allyl- and benzyl-xanthates gives 5,6-cellulosene. Some thiocarbonyl derivatives of polysaccharides have been prepared. "... 

Thermolysis of the camphor derivative (239) in the gas phase yielded the ring-expanded compound (240 65 %) by ene retrogression followed by intramolecular aldol condensation and dehydration of the intermediate keto-aldehyde. Pyrolysis in the condensed phase, however, converted (239) into (241 100%) by dehydration (loss of tertiary OH) and [1,5] sigmatropic H-shift in the a-vinyl-enol intermediate. The retro-ene mechanism is also involved in the pyrolytic conversion of allyl sulphides, e.g. (242), into thiocarbonyl compounds, e.g. thiocamphor. The flash thermolysis of... 

A variation of the use of thiourea for converting alkyl halides into thiols uses N-acetylthiourea although reaction with an alkyl halide in refluxing EtOH is slow, a separate hydrolysis step is not required and the method may prove useful for the synthesis of water- or alkali-sensitive thiols. Other methods based upon thiocarbonyl derivatives are exemplified by the addition of allylic Grignard reagents to thioketones, giving 7-unsaturated... 

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