A New Synthesis of β-Keto Phosphonates and β-Keto Silanes

Article abstract of DOI:10.1021/jo00373a003

A new preparation of β-keto phosphonates from α-bromo ketones, by reaction of dialkyl chlorophosphate electrophiles with the dilithiated derivative of the bromo ketone, is described.This umpolung approach is complementary to the classical Arbuzov synthesis in two important ways.It extends the range of possible ketone substrates, allowing use of secondary α-halo ketones or α-bromo ketones where the Arbuzov reaction often fails.It also extends the variety of phosphonates available, by allowing, for example, the direct preparation of bis-(trifluoroethyl)phosphonates.These fluoroalkyl phosphonates are not readily available via the Arbuzov reaction,because tris(trifluoroethyl) phosphite is only weakly nucleophilic.From our efforts to employ (trialkylsiloxy)vinyl bromides and n-butyllithium to generate an intermediate vinyllithium reagent, in place of forming the lithium enolate and using tert-butyllithium, a facile migration of trialkylsilyl groups from oxygen to the α-carbon has been discovered.This has been exploited in the development of a new route from α-bromo ketones to α-trialkylsilyl ketones.