On the Reactivity of α-(Triphenylphosphoranylidene)-benzylphenylketene with Nitrogen Compounds: Synthetic and Mechanistic Implications

Abstract

A reatividade do ilídeo de fósforo estabilizado derivado da difenilciclopropenona, o α-(trifenilfosforanilideno)-benzilfenilceteno, frente a compostos nitrogenados polifuncionalizados foi investigada. Em particular, a reação do α-(trifenilfosforanilideno)-benzilfenilceteno com o azodicarboxilato de etila pode se constituir como um novo método de síntese de N-acil-carbamatos densamente substituidos. The reactivity of α-(triphenylphosphoranylidene)-benzylphenylketene, a stabilized phosphorus ylide derived from diphenylcyclopropenone, toward nitrogen compounds was investigated. Particularly, the reaction of diethyl azodicarboxylate with α-(triphenylphosphoranylidene)benzylphenylketene provides a new route to polysubstituted N-acyl carbamates.

The chemistry of enaminones, diazocarbonyls and small rings: our contribution

“…The products formed are presented in Scheme 29 In each case triphenylphosphine was also recovered. 65 From a mechanistic viewpoint, the formation of 107-111 may be visualized as occurring through attack of the nitrogen nucleophile at the electrophilic carbon of the ketene portion of α-TBPK, followed by triphenylphosphine elimination and proton transfer (Scheme 30). The presence of this good leaving group changes the direction of the reaction when compared to the reaction of the parent 8a as shown in Scheme 24.…”

A Bioorthogonal Ligation of Cyclopropenones Mediated by Triarylphosphines

“…Ketene ylides can be long-lived and even isolated under ambient, moisture-free conditions . However, these moieties are susceptible to rapid reaction with both oxygen and amine nucleophiles. ,− We hypothesized that intermediate 1 could be formed under aqueous conditions and competitively trapped with strong nucleophiles (e.g., amines) even in the presence of water. The selectivity could be further enhanced by tethering the desired nucleophile to the phosphine core or using an excess of an exogenously delivered probe.…”

“…The reaction also proceeded efficiently when the ketene ylide was preformed and stored for 24 h prior to the addition of isopropylamine (Figures S11–S13). Consistent with the proposed mechanism, lower catalyst loading slowed the reaction but did not significantly impact the overall yield (entry 2).…”

Phosphine-Catalyzed Stereoselective Ring-Opening Addition of Cyclopropenones with Nucleophiles

“…Based on the literature, ,, a possible mechanism is depicted in Scheme . Taking the formation of 3a , for example, the phosphine first attacks the electrophilic cyclopropenone 1a followed by ring cleavage to form the α-ketenyl ylide intermediate A .…”

“…For its reactivity toward nucleophiles (NuH), Prescher and co-workers , have reported the phosphine-mediated addition of cyclopropenones with amines for applications in elegant bioorthogonal ligations (Scheme b, up). However, the comprehensive study of this ring-opening addition reaction remains elusive in terms of the scope and mechanism. ,, Stemming from our interest in Lewis base catalysis, ,, we, here, report the systematic investigation on this phosphine-catalyzed ring-opening addition reaction of cyclopropenones with nucleophiles. The results show that the reaction accommodates a vast range of nucleophiles, including oxygen-, nitrogen-, sulfur-, and carbon-based ones, and proceeds under very mild conditions using only 1 mol % PPh 3 catalyst at room temperature.…”