Alkenes from episulfides

IS) By ethyl cyanoacetate. Attempted base-catalyzed condensations of ethyl malonate and ethyl acetoaoetate -with the simple episulfides have been unsuccessful. However, 2-iminothioplianes are obtainable from ethyl cyanoacetate and alkene sulfides.108 In the alkylation of ethyl cyanoacetate with propylene sulfide and isobutylene sulfide, mjcloophilic attack by the carb nion is on the primary carbon atom of the episulfide (Eq. 53). 

Episulfides, generated from diazo compounds and a thioketone, can also undergo desulfurization with phosphines to give alkenes (see section 4.3.7). 

In other reactions the sulfur atom is removed from CS2 by olefins probably as an alkene episulfide but this is not certain,3lb e.g.,... 

The episulfidation of alkenes and allenes is believed to proceed in a similar manner (881,882). Here there is also a secondary reaction, but in this instance it is noninnocent, in that the molybdenum(V) dimer, [MoO(p-S)(S2CNEt2)]2, and tetraethylthiuram disulfide are formed. This is especially noticeable when less reactive (Z)-cycloalkanes are used, and the authors suggest that while initial sulfur transfer is facile, transfer from [MoOS(S2CNEt2)2] proceeds at a slower rate, allowing the internal redox reaction to become a dominant pathway. 

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