Science of Synthesis

Chiba, S.; Narasaka, K., Science of Synthesis Knowledge Updates, (2011) 4, 474.

Nucleophilic addition to oxime derivatives with organometals is somewhat difficult because oximes are often less electrophilic than the corresponding imines, due to the conjugation of the O-electron pair to the C=N π-bond. General problems are proton abstraction at the α-position, the existence of mixtures of E/Z-isomers, and the lability of the O—N bond. Accordingly, modification of the organometallic reagents is required in order to decrease their basicity, e.g. combination of alkyllithiums with boron trifluoride–diethyl ether complex. O-Alkylformaldehyde oximes have been used to introduce aminomethyl groups to organometals.[‌421‌–‌424‌] Organolithium reagents add to α-alkoxyimino carboxylic acid derivatives, which provides a direct method for the synthesis of N-hydroxy-α-amino acids. α-Aminomethylation of esters and amides is achieved by the reaction of their lithium or magnesium enolates with O-alkylaldoximes.[‌421‌] By the reactions with lithium enolates of esters, N-alkoxy-β-lactams ‌48‌ can be obtained via cyclization of the resulting α-amino esters (‌Scheme 40‌). β-N-Hydroxyamino acid derivatives are obtained by the reactions of ketene silyl acetals with aldoximes in the presence of a catalytic amount of tri­meth­ylsilyl trifluoromethanesulfonate.[‌421‌]

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M-[8-(8,8-Meeeeeeeeeeeeee)eee-8-eeee]eeeeeeeeeeeee (‌88‌); Meeeeee Meeeeeeee:[‌888‌]

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