作者:John F. O'Connell、Jonathan Parquette、William E. Yelle、Wilhelm Wang、Henry Rapoport
DOI:10.1055/s-1988-27702
日期:——
Three syntheses of methyl 1-methyl-2,4-dibromo-5-imidazolecarboxylate (8) are presented. One proceeds from sarcosine via ring closure, bromination, and desulfurization. The second uses N-methylimidazole, polybromination, and selective halogen-metal interchange. The third and most efficient and preparatively useful route begins with diaminomaleonitrile (13). Ring closure with triethyl orthoformate followed by methylation and hydrolysis affords 1-methyl-4,5-imidazoledicarboxylic acid (16). Regioselective decarboxylation followed by esterification yields methyl 1-methyl-5-imidazolecarboxylate (18). Subsequent dibromination gives the completely substituted imidazole 8. The primary purification in this sequence is fractional sublimation of 18 after the esterification step. An overall yield of 26% is achieved from diaminomaleonitrile (13) to methyl 1-methyl-2,4-dibromo-5-imidazolecarboxylate (8), which is a key intermediate for the synthesis of tricyclic imidazo cooked food mutagens.
介绍了三种合成甲基1-甲基-2,4-二溴-5-咪唑甲酸酯(8)的方法。第一种方法是通过肌氨酸的环化、溴化和脱硫步骤进行。第二种方法使用N-甲基咪唑、多溴化和选择性卤素-金属互换。第三种方法最为高效且实用,始于二氨基富马腈(13)。通过三乙基原甲酸酯进行环化,随后甲基化和水解得到1-甲基-4,5-咪唑二羧酸(16)。区域选择性脱羧后再酯化得到甲基1-甲基-5-咪唑甲酸酯(18)。后续的双溴化得到完全取代的咪唑8。在此序列中主要的纯化步骤是酯化步骤后的分馏升华。从二氨基富马腈(13)到甲基1-甲基-2,4-二溴-5-咪唑甲酸酯(8)的总收率为26%,后者是合成三环咪唑熟食诱变剂的关键中间体。