School of Chemistry, University of Nottingham, University Park, Nottingham NG7 2RD, UK.
J Org Chem. 2010 Jan 1;75(1):152-61. doi: 10.1021/jo902256r.
Dirhodium tetraacetate catalyzed reaction of alpha-diazo-beta-keto-carboxylates and -phosphonates with arenecarboxamides gives 2-aryloxazole-4-carboxylates and 4-phosphonates by carbene N-H insertion and cyclodehydration. In stark contrast, dirhodium tetrakis(heptafluorobutyramide) catalysis results in a dramatic change of regioselectivity to give oxazole-5-carboxylates and 5-phosphonates. Alpha-diazo-beta-ketosulfones behave similarly and give 5-sulfonyloxazoles upon dirhodium tetrakis(heptafluorobutyramide) catalyzed reaction with carboxamides. The analogous reactions of thiocarboxamides give the corresponding thiazole-5-carboxylates, -phosphonates, and -sulfones.
二钌四乙酸催化的α-重氮-β-酮羧酸酯和膦酸酯与芳酰胺的反应，通过碳烯 N-H 插入和环脱水反应生成 2-芳基恶唑-4-羧酸酯和 4-磷酸酯。相比之下，二钌四(全氟丁酰胺)催化则导致反应的区域选择性发生显著变化，生成恶唑-5-羧酸酯和 5-磷酸酯。α-重氮-β-酮亚砜的反应行为类似，在二钌四(全氟丁酰胺)催化下与酰胺反应生成 5-磺酰基恶唑。类似的硫代酰胺反应生成相应的噻唑-5-羧酸酯、膦酸酯和亚砜。
