Alkylidenephosphoranes reactions, review

Alkylidenephosphoranes have recently achieved great importance by their use in Wittig olefination. The manifold applications of that reaction are supplemented by the reactions involving introduction of acyl or alkyl groups the latter have been reviewed by Bestmann.455-457 It should be noted that,... 

Alkylidenephosphoranes (a.La. phosphorus yUdes) of the general formula Ph3P=CR R (1) have been frequently used in key steps of heterocycle synthesis. Numerous papers and review articles [1-4] testify their versatility in the construction of rings with sizes ranging from three to well beyond 20 and with virtually any number, kind and distribution of heteroatoms. The Wittig alkenation of carbonyl groups is doubtless the most common, though not the only, reaction of P-ylides that has been employed in the cyclization of bifunctional precursors. The cycloaddition between acyl ylides (1 = H,... 

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