Dienes thioethers, cyclic

Triazines are generally more reactive in [2 + 4] cycloaddition in comparison with 1,2,3-tria-zines. The wide variety of dienophiles can be employed enamines, enaminones, vinyl silyl ethers, vinyl thioethers, cyclic ketene jV,O-acetals, /V-phenylmaleimide, 6-dimethylaminopentafulvene, 2-alkylidene-imidazolidines (cychc ketene aminals), cyclic vinyl ethers, arynes, benzocyclopropene, acetylenes, and alkenes like ethylene, (Z)-but-2-ene, cyclopentene, cyclooctene and bicyclo[2.2.1]hept-2-ene, hexa-1,5-diene, cycloocta-1,5-diene, diallyl ether, cyclododeca-l,5,9-triene,... 

Still another related method consists in reacting dienes with dimethyl disulphide in the presence of iodine, to produce the corresponding bis(o ,/J-dmiethylmercapto) derivative241-243. Again, characteristic fragmentation is obtained in the standard El spectra. However, this method involves complications if the double bonds are separated by less than four methylene groups due to the formation of cyclic thioethers. 

We have found that metathesis of olefmic sulfides can be successfully achieved by using, as homogeneous catalyst, the aryloxy(chloro)neopentylidene-tungsten complex 1. Thus, the self-metathesis of allyl methyl sulfide (4) and of 5-dkylthiocycloooctenes (5) (or their cometathesis with various acyclic or cyclic olefins without functional groups) can lead to a family of new olefins, dienes, or unsaturated polymers containing one or more thioether groups. 

The Michael addition of cyclic ketones to l,3-diene-l,l-dicarboxylates ArCH= CHCH=CH(C02R)2> catalysed by the proline-derived salt (252), has been reported to proceed in a 1,4- (rather than 1,6-) manner with 45-80% ee and <83 17 drP More successful was the proline thioether (253), which under solvent-free conditions was able to catalyse the 1,4-addition of ketones R CH2COR to monohaloalkenes ArCH=C(X)CH=CHN02 with up to >99% ee and >99 1 dr ... 

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