Alkylidene cyclopropanes, synthesis

The synthesis of alkylidene cyclopropanes and cyclobutanes involving seleno compounds has been achieved via three different routes which involve... 

Methylselenoxy analogs are even more difficult to react and treatment of the corresponding methylseleno derivative at 80 °C with terf-butyl hydroperoxide/basic alumina (conditions which proved particularly efficient for the synthesis of terminal olefins from methyl selenides bearing a methylseleno group at the terminus of the alkyl chain 7,8,12>, which are more difficult to react) as expected 140) does not lead 35) to the desired alkylidene cyclopropanes but to low yields of cyclobutanones resulting probably from the well-known 140) reaction of rert-butyl hydroperoxide with the alkylidene cyclopropane formed transiently35). 

Syntheses of Alkylidene Cyclopropanes and Cyclobutanes by formal Elimination of a Hydroxyl Group and a Heteroatomic Moiety The methods discussed above, although efficient, possess important limitations. They do not permit, for example, the synthesis of tetrasubstituted alkylidene cyclopropanes due to the unavailability of the starting selenides, the alkylation of a-selenocyclopropyllithiums with sec-alkylhalides being not feasible at present. 

These 1-seleno-l-vinylcyclopropanes have proved especially useful, inter alia, for the synthesis of allyl alcohols where the carbon-carbon double bond is part of an alkylidene cyclopropane 4S) and for the preparation of allylidene cyclopropanes45, (see page 52). 

The reactions reported for the synthesis of alkylidene cyclopropanes from l-(l-Silyl)... 

The novel reagents which have been introduced for the synthesis of alkylidene cyclopropanes from (P-hydroxyalkyl) methylselenides proved particularly efficient for the synthesis of a large variety of olefins, including other alkylidene cycloalkanes . PI3 or PjI /NEtj are also to transform (p-hydroxyalkyl) sulfides to olefins but Instead lead to a stable l-(l-phenylthio)-l-(iodomethyl) cyclopropane starting from l-(l-phenylthio)-(hydroxymethyl)cyclopropane (scheme 46) The reaction of... 

Synthese of Alkylidene cyclopropanes Via the Selenoxide Route The synthesis of olefins by oxidative elimination of selenides is one of the most versatile and useful methods in selenium chemistry reaction usually... 

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