Sequential In Situ-Formed Kukhtin–Ramirez Adduct and P(NMe₂)₃-Catalyzed O-Phosphination of α-Dicarbonyls with P(O)–H

Abstract

O-Phosphination of α-dicarbonyls via sequential in situ formation of a Kukhtin−Ramirez adduct and a P(NMe 2 ) 3catalyzed process has been exploited for the synthesis of αphosphoryloxy carbonyls. A range of P(O)−H derivatives, including diarylphosphine oxides, arylphosphinates, and phosphinates, are competent candidates to be introduced into the αdicarbonyls in this transformation, and various α-phosphoryloxy carbonyls are obtained. This approach possesses advantages of mild conditions, simple operations, atom economy, high efficiency, and gram-scale synthesis, which make it promising in the synthesis toolbox.

Synthesis of oxime ethers via a formal reductive O–H bond insertion of oximes to α-keto esters

“…Based on the above results and the literature, 12 a plausible reaction pathway is proposed in Scheme 3. Formal [4+1] cycloaddition of 1a and P(NMe 2 ) 3 led to the formation of Kukhtin–Ramirez adducts C and D (KRAs).…”

“…Therefore, KRAs have received attention as highly useful carbene surrogates that can sequentially react with an electrophile and a nucleophile, such as in [2+1] and [4+1] cycloaddition reactions 11 and X–H bond insertion reactions (O–H/N–H/S–H/P–H). 12 Although O–H bond insertion using acidic carboxylic acids and phenols has been well investigated, there are no studies reporting the reaction of KRAs with oximes. Intrigued by the attractive reactivity of the KRAs and motivated by the challenging goal of synthesizing oxime ethers, we hypothesized that a trivalent phosphorous reagent-mediated diazo-free O–H bond insertion between oximes and α-keto esters would provide a simple and practical protocol to construct oxime ethers.…”

Challenges and Breakthroughs in Selective Amide Activation

“…In a related approach, Huang et al. reported a [4+2]‐annulation with N ‐aryl amides 11 and alkenes 12 to afford 3,4‐dihydroquinolines 13 (Scheme 3B) [13] . The authors also reported that a reductive work up is able to directly yield valuable tetrahydroquinolines 14 in high yields.…”

O–H Insertion of Hydrogenphosphate Derivatives and α-Diazo Compounds

“…To the best of our knowledge, there is no other case of such an O–H insertion under mild conditions. Very recently, Zi and co-workers achieved the P­(NMe 2 ) 3 -catalyzed O -phosphination of α-dicarbonyls with H-phosphine oxides via a Kukhtin–Ramirez adduct intermediate, and a broad scope of α-phosphoryloxy carbonyls was synthesized with simple operations . Herein, we disclosed the catalyst-free insertion of hydrogenphosphate derivatives and α-diazo compounds, which allowed a facile and straightforward route to a wide range of α-phosphoryloxy skeletons under mild conditions with satisfactory yields (Scheme d).…”