Diethyl chlorophosphate

(A) A series of enol phosphates were synthesized starting from 2-substituted acetophenones. The ability of these compounds to undergo cross-coupling reactions in the presence of various heteroatoms, makes the enol phosphate an attractive functional group for the construction of various substituted heterocyclic systems via ring-closing methathesis. (B) A new practical synthetic method for the preparation of vinyl halides from acyclic and cyclic ketones and imides via the corresponding phosphate intermediates is proven. This process is satisfactory in an industrial scale production since the work-up procedure is easy to operate. Moreover, this method is applied to the industrial production of SUN N4057, a pharmaceutical candidate for the treatment of cerebral infarction. (C) A total synthesis of the silphinene IV, a natural product, has been accomplished in 12 steps. Since attempts to trap the ketone as its silyl enol ether in the cleavage reaction were unsuccessful, a study of the enolate formation of I was undertaken in hopes of selectively forming enol phosphate II as the direct precursor to silphinene. Termodynamic enolization of I and quenching with DECP rendered enolphosphate II as major product. Reduction of this mixture, gave a mixture of silphinene IV and isosilphinene V. An efficient and regioselective formation of enol phosphate II, served to prepare the (±)-silphinene IV with high selectivity. (D) Monophosphorylated hydroxyphenols, which can be used as flame retardants in polycondensation reactions due to their free hydroxy group, were synthesized. The phosphorylation of hydroquinone I by DECP gave predominantly the monophosphate II. (E) DECP is used in the oligonucleotides synthesis via N-unprotected methods. The basis of this method is the activation of an hydroxyl group as an alkoxide which undergoes the O-selective reaction with DECP to give the nucleoside phosphate in almost quantitative yields. © Georg Thieme Verlag Stuttgart.