The reaction of keto-stabilized sulphonium and arsonium ylides with α-chlorooximes

Recent advances in the application of ylide-like species in [4 + 1]-annulation reactions: an updated review

“…The first example of [4 + 1]-annulation involving these Michael acceptors and sulfonium ylides was demonstrated by Ticozzi et al in 1972. 24 This method was further developed by Wang et al 25 Thus, the reac-tion of α-halooximes with keto-stabilized sulfonium ylides 4 in the presence of sodium carbonate delivered disubstituted isoxazolines 31 (Scheme 12). It should be noted that the ylide 4 could be generated in situ from the corresponding sulfonium salt 10 or taken in a free form.…”

Conjugated nitrosoalkenes as Michael acceptors in carbon–carbon bond forming reactions: a review and perspective

“…There are several sources of α-nitrosoalkenes as shown in Scheme 1 . Conventional precursors of α-nitrosoalkenes are α-halooximes 1 (or halo-substituted nitroso compounds [ 11 – 12 ]), which undergo deprotonation/halide elimination upon treatment with a base [ 13 ] ( Scheme 1 , reaction (1)). A disadvantage of this method is that NSA are generated fast and high stationary concentrations are achieved facilitating polymerization.…”

“…C-Nucleophiles possessing leaving groups have been also used in the construction of N–O heterocycles using nitrosoalkenes as intermediates. An early example is the reaction of sulfonium ylides 92 with α-halo ketoximes 1 leading to isoxazolines 93 reported by Bravo [ 11 ] and Gilchrist [ 83 ] ( Scheme 35 ). The process is believed to proceed via the generation of a nitrosoalkene intermediate ( NSA ) followed by a formal [4 + 1]-annulation reaction with ylide (tandem Michael addition/intramolecular nucleophilic substitution of dimethylsulfide by oximate anion in intermediate 94 ).…”

“…Triphenylarsonium ylides were also studied in the reaction with nitrosoalkenes, yet lower yields of isoxazolines 93 were obtained as compared to sulfonium ylides [ 11 ].…”

Five‐Membered Heterocycles: 1,2‐Azoles. Part 2. Isoxazoles and Isothiazoles

“…The process is thought to involve a [4 þ 1] cycloaddition of the transient nitrosoalkene with isocyanides to give 73. The C synthon can also be a keto-stabilized sulfonium ylide, as illustrated by the reaction of benzoylsulfonium ylide with (2-chloro-2-ethoxy-1-nitrosoethyl)benzene leading to isoxazole 74 [172].…”