A New Multicomponent Reaction Catalyzed by a [Lewis Acid]⁺[Co(CO)₄]^- Catalyst: Stereospecific Synthesis of 1,3-Oxazinane-2,4-diones from Epoxides, Isocyanates, and CO

The use of mechanistic information to develop a new, catalytic multicomponent reaction is described. The complex [(salph)Al(THF)2]+[Co(CO)4]- (1, salph = N,N‘-o-phenylenebis(3,5-di-tert-butylsalicylideneimine), THF = tetrahydrofuran), which is known to carbonylate epoxides, aziridines, and β-lactones, was used to catalyze the synthesis of 1,3-oxazinane-2,4-diones from epoxides, isocyanates, and CO. Under optimized conditions, the reaction was both selective and high-yielding. 1,3-Oxazinane-2,4-diones were synthesized from a variety of epoxides and isocyanates, including some epoxides that do not undergo simple ring-expansion carbonylation. The best results were obtained using highly electrophilic isocyanates. The mechanism of the multicomponent reaction was investigated using labeling and stereochemistry, and the data obtained were consistent with the 1-catalyzed formation of β-lactone and 1,3-oxazinane-2,4-dione from a common intermediate.本研究报道了基于机理信息开发新型催化多组分反应的相关工作。已知金属配合物[(salph)Al(THF)₂]⁺[Co(CO)₄]⁻（1，其中salph为N,N'-邻亚苯基双(3,5-二叔丁基水杨醛亚胺)，THF为四氢呋喃（tetrahydrofuran））可实现环氧化物、氮丙啶与β-内酯的羰基化反应，本研究将该配合物用于催化环氧化物、异氰酸酯与一氧化碳（CO）合成1,3-恶嗪烷-2,4-二酮。在优化后的反应条件下，该反应兼具优异选择性与较高产率。通过多种环氧化物与异氰酸酯均可合成1,3-恶嗪烷-2,4-二酮，底物范围甚至涵盖部分无法发生简单开环羰基化的环氧化物；当采用高亲电性异氰酸酯时，可获得最佳反应结果。本研究通过同位素标记与立体化学分析对该多组分反应的机理展开了探究，所得实验数据表明，配合物1可经由共同中间体催化生成β-内酯与1,3-恶嗪烷-2,4-二酮。