Alkenyl phosphates, formation

The allylstannane 474 is prepared by the reaction of allylic acetates or phosphates with tributyltin chloride and Sml2[286,308] or electroreduction[309]. Bu-iSnAlEt2 prepared in situ is used for the preparation of the allylstannane 475. These reactions correspond to inversion of an allyl cation to an allyl anion[3l0. 311], The reaction has been applied to the reductive cyclization of the alkenyl bromide in 476 with the allylic acetate to yield 477[312]. Intramolecular coupling of the allylic acetate in 478 with aryl bromide proceeds using BuiSnAlEti (479) by in situ formation of the allylstannane 480 and its reaction with the aryl bromide via transmetallation. (Another mechanistic possibility is the formation of an arylstannane and its coupling with allylic... 

A BINAP-Pd complex catalyzes a highly enantioselective C-C bond formation between an aryl triflate and 2,3-dihydrofuran (eq 22). The intramolecular version of the reaction using an alkenyl iodide in the presence of PdCl2[(/J)-BINAP] and Silver(I) Phosphate allows enantioselective formation of a bicyclic ring system (eq 23). ... 

Study of the photolytic behaviour of triaryl phosphates has been further extended new model substrates examined include tri-l-naphthalenyl, tri-9-anthracenyl, and tri-8-quinolinyl phosphates, together with some of their methoxy derivatives and analogous dialkyl aryl and alkyl diaryl esters. Noted reactions include aryl migrations with the formation of, for example, l-[2-(l-naphthalenyl)-naphthalenyl] phosphate, in substantial amounts, together with appropriate biaryls. A preliminary report describes the photolysis of methyl alkenyl aryl phosphates (58) which undergo transformation along more than one pathway. The isolated products from (58) (R = OMe, = Me) were (60),... 

Alkenyl-aluminium or -zinc species cross-couple with allylic halides or derivatives of allylic alcohols (c.g. acetates or phosphates) under the influence of Pd(PPh3)4 to give 1,4-dienes. In favourable examples coupling occurs with complete retention of stereo- and regio-chemistry of both alkenyl and allyl substrates, and it is free from formation of homocoupled products (Scheme 73). However, partial allylic inversion was observed in reactions involving E-crotyl... 

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