Hydrohalogenation Reaction of Substituted 1,2-Allenic Carboxylic Acids,Ester,Amides,Nitriles,and Diphenyl Phosphine Oxides

摘要

The hydrohalogenation reaction of 1,2-allenic carboxylic acids,esters,amides,nitriles,and diphenyl phosphine oxides with HX or MX(X=I,Br,Cl,M=Na,Li) in different solvents,such as HOAc,CF_3CO_2H, andCF_3CO_2H-HOAc (1:) was studied.The reaction is a nucleophilic conjugate addition in nature and provides efficient entries to 3-halo-3-enoic acids,esters,amides,nitriles,and 2-haloallyl diphenyl phosphine oxides.The #beta#,#gamma#-over #alpha#,#beta#-selectivity and stereoselectivity depend on the solvent(s) and the temperature applied. In most cases,the Z- and E-isomers can be easily separated by chromatography on silica gel.The subsequent cross-coupling reaction with organometallic reagents and terminal alkynes showed the synthetic potential of these products.