Silyl phosphites. 16. Mechanism of the Perkow reaction and the Kukhtin-Ramirez reaction. Elucidation by means of a new type of phosphoryl rearrangements utilizing silyl phosphites

Abstract

Reactions of -lithiated diethyl a-[(trimethylsilyl)oxy]benzylphosphonate (4) with benzoyl chloride and chloroiodomethane afforded benzoylated and chloromethylated products (1 and 2) corresponding to the 1:1 carbonyl adducts of diethyl trimethylsilyl phosphite with benzil and phenacyl chloride which were not obtained by the reactions between the phosphite and benzil or phenacyl chloride. Pyrolysis of 1 and 2 afforded 1,3,2-dioxaphosphole (6) and enol phosphate (8). On the other hand, treatment of 1 and 2 with tetrabutylammonium fluoride afforded benzoin phosphate (7) and 1,2-epoxy phosphonate (14), respectively, as the main products. These results are also discussed in connection with the mechanism of the Perkow reaction and the Kukhtin-Ramirez reaction.

Comparative Computational Study on the Reaction of Chloroacetone with Trimethylphosphite: Perkow versus Michaelis–Arbuzov Reaction Paths

“… , Despite the paramount importance of this reaction, no quantum chemical study concerning its mechanism has been reported so far. The abnormal Michaelis–Arbuzov reaction between α-halocarbonyl compounds and phosphites to give enol (vinyl) phosphates ( II ) (Scheme ) is known as the Perkow reaction after the pioneering work of Perkow in 1952. , Very many examples have been reported since then, , including their inclusion in cascade reactions such as the Nef isocyanide/Perkow sequence. − A variety of mechanistic proposals have been suggested for this reaction including the initial attack of the nucleophilic P atom to the carbonyl C − or O atoms, the α-carbon atom ,− or the α-halogen atom. − More recent computational studies of the Perkow-type reaction between a cyclic phosphite ester and chloral − show that the process starts by a chelotropic cycloaddition of the P atom to the carbonyl CO bond furnishing a σ 5 ,λ 5 -phosphorus three-membered ring intermediate II . Two located diastereomeric transition states (TS) corresponding to this chelotropic step were erroneously assigned to the ring expansion final step.…”

Organocatalytic Arylation of α‐Ketoesters Based on Umpolung Strategy: Phosphazene‐Catalyzed SNAr Reaction Utilizing [1,2]‐Phospha‐Brook Rearrangement

“…Whereas the reaction generally requires a stoichiometric amount of a Brønsted base for generating an anionic nucleophile, catalytic variants have also been developed by using silylated pronucleophiles with fluoroarenes as the electrophile under the influence of a catalytic amount of a Lewis base . Thus, we designed a new catalytic system for the S N Ar reaction of a carbanion generated through the umpolung process by using a silylated phosphite . Specifically, we intended to develop a reaction of ester enolates generated from α‐ketoesters with fluoroarenes, providing α‐hydroxyester derivatives.…”

“…[6] Thus,w ed esigned an ew catalytic system for the S N Ar reaction of ac arbaniong enerated through the umpolung process by using as ilylated phosphite. [7] Specifically,w ei ntended to develop ar eaction of ester enolates generated from a-ketoesters with fluoroarenes, providing a-hydroxyester derivatives. Our proposed reactionsystem is shown in Scheme1.…”

Preparation of Regioselectively Protected Hydroquinones by Phosphorylation of p‐Benzoquinones with Trialkyl Phosphites

“…The preferred formation of 6a from 4a and 16 from 5 is therefore due to the conjugation of the methoxy-lone-pairs with either the quinoid or the aromatic nucleus of these systems, and corresponds to the selectivity expected for a nucleophilic phosphorylation agent. These results allow, however, no decision, whether an ionic mechanism with phosphite as attacking species [la] [39] or a radical mechanism [35] is involved, since a phosphinium radical s, generated together with semiquinone t in a redox process from 1 and phosphite, could have nucleophilic properties in analogy to carbon-centered radicals substituted with alkoxy groups [40a] (Scheme 8 ) 27). The phosphonates isolated from the reactions of 4a, 4f, 4h, 4i, and 5 show that the C-phosphorylation of p-benzoquinones affords exclusively the regioisomers expected for a nucleophilic 1,4-addition.…”