Formation of 1-bromocarbonylindazoles via cleavage of 4-bromo ortho-substituted arylsydnones with HBr
摘要:
Treatment of 4-bromo-3-arylsydnones containing an ortho-carbonyl substituent (cf. 1d-j) with HBr gas leads to the corresponding, novel 1-bromocarbonyl-3-substituted indazoles (2d-k), generally in excellent yield.
Sydnone Ring as an ortho-Director of Lithiation, 3: One-Pot Regiospecific o-Acylation and Subsequent Sydnone 4-Substitution
摘要:
Readily available 3-phenylsydnone (1) reacts with n-butyllithium/N,N,N',N'-tetramethylethylenediamine (TMEDA) to form the dilithio species 2, which can be acylated regiospecifically at the ortho-aryl position using N-methoxy-N-methylamides (Weinreb's amides) followed by reaction with a second, more reactive electrophile at the sydnone C-4 position. Asymmetrically substituted arylsydnones 7 are obtained in 57-86% yield.