Michael Addition of P-Nucleophiles to Conjugated Nitrosoalkenes

Abstract

A general approach to various α-phosphorussubstituted oximes (β-oximinoalkyl-substituted phosphonates, phosphine oxides, phosphine−borane complexes, and phosphonium salts) was developed. The strategy exploits hitherto unknown Michael addition of PH-containing compounds (diphenylphosphine oxide, diisopropyl phosphite, phosphine− borane complexes, and triphenylphosphonium bromide) to unstable conjugated nitrosoalkenes, which are generated in situ from corresponding nitrosoacetals. The resulting α-phosphorus-substituted oximes can be considered as useful P-, N-, and O-ligands for catalysis and precursors to valuable βaminophosphonates.

Umpolung of Enamines: An Overview on Strategies and Synthons

“…Unlike, nitroalkenes, nitrosoalkenes NSA (Scheme 5a) are unstable species that tend to polymerize and undergo side reactions. 26 Nevertheless, these intermediates have been successfully used in Michael additions with many nucleophiles, such as C-H active compounds, 27 organocopper compounds, 28 amines, 27c,29 phenols, 30 carboxylic acids, 30 thiols, 30b,31 dialkylphosphonates, 32 phosphine-borane complexes, 32 and cyanide 33 and azide anions, 34 among others 27c,35 (Scheme 5b). These reactions produce -substituted oximes that can be readily converted into the corresponding carbonyl compounds, amines, or hydroxylamines.…”

C−H Reactivity of the α‐Position in Nitrones and Nitronates

“…A more convenient way to access α‐substituted oximes from nitronates is transformation of the latter into stable N , N ‐bis(oxy)enamines 13 and 15 followed by their reaction with nucleophiles (Scheme ). Importantly, enamines 13 and 15 are able to react with N‐, O‐, S‐ and P‐nucleophiles taken in their H‐forms (amines, carboxylic acids, phenols, thiols, thiophenols, dialkyl phosphites, etc.) without the need for any additives, as exemplified in Scheme .…”

Synthesis of Bis(β‐Oximinoalkyl)malonates and Their Catalytic Reductive Cyclization to Piperidines

“…Due to instability of NSA and tendency towards polymerization, the nature of precursor is crucial for a successful coupling with nucleophiles. [17] As seen in Table 1, the desired unsymmetrical bisadduct 2 ab was formed efficiently when using enenitrosoacetal 5 b, while other NSA precursors gave poor yields (Table 1, entries 1, 4-7). The amount of DBU could be reduced to 1 equiv.…”