Lithiated oxygen heterocycles

This survey describes how the chemistry of lithiated oxygen heterocycles has been fruitfully exploited, particularly over the last 10 years, for the preparation of more (stereodefined) functionalized derivatives and products derived from them. Also, how they have contributed to natural product synthesis and molecules of relevant pharmaceutical interest. The genesis of the reactive lithiated intermediates (especially a- and orf/io-lithiated (hetero)arylepoxides, -oxetanes and -tetrahydrofurans) requires a careful choice of the experimental conditions in terms of solvents and temperature in order them to be successfully intercepted by electrophiles. The study of the aggregation and solvation of certain chiral functionalized lithiated oxygen heterocycles has provided further hints about the factors affecting their configurational stability and... 

Recent Developments in the Lithiation Reactions of Oxygen Heterocycles... 

The synthesis of oxygen- and nitrogen-containing heterocyclic compounds by anionic cyclization of unsaturated organolithium compounds has been reviewed recently. " Broka and Shen reported the first intramolecular reaction of an unstabilized a-amino-organolithium compound using reductive lithiation of an A,5-acetal derived from a homoaUylic secondary amine (Scheme 21). Just one example was reported treatment with lithium naphthalenide gave the pyrrolidine product, predominantly as the cis isomer. 

A number of techniques are available for the one-pot conversions of carbonyl substrates to thiiranes. These entail the addition of a lithiated thiol derivative to the substrate, transfer of either an acyl group or heterocycle to the oxygen atom, and cyclization. A recent example is depicted in Scheme 19. ... 

Scheme 1-128. 2-Lithiated 4//-5,6-dihydropyran and benzofuran undergoing metal-assisted opening of the heterocyclic ring by oxygen displacement.

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