MgI2-Mediated Ring Expansions of Secondary Methylenecyclopropyl Amides
摘要:
Ring expansion of secondary methylenecyclopropyl amides in the presence of MgI2 was investigated. Various isomeric five-membered unsaturated lactams were obtained, depending on the character of the substituent Q. The amide group served as a nucleophile in ring closing as well as an activator for ring opening. In the presence of a variety of aryl aldimines or aldehydes, alkylative ring expansion occurred in a single step under mild and neutral conditions leading to gamma'-amino- or -hydroxy-alkylated pyrrol-2-ones. Also, it was shown that a 4-methylpyrrol-2-one could be transformed to a gamma-hydroxy-alkylated product by the use of a direct vinylogous aldol reaction.
Synthesis of Highly Functionalized Pyrrolidines via a Selective Iodide-Mediated Ring Expansion of Methylenecyclopropyl Amides
作者:Mark E. Scott、Mark Lautens
DOI:10.1021/jo802049u
日期:2008.11.7
iodide-mediated, tandem Mannich/cyclization to afford trans-2,3-disubstituted pyrrolidines from methylenecyclopropyl amides in good to excellent yields and selectivities. The reaction scope has been drastically expanded to include a wide array of aromatic, heteroaromatic and alpha,beta-unsaturated imines, as well as a variety of methylenecyclopropyl amides. Additionally, mechanistic studies were carried out
Divergent Selectivity in MgI<sub>2</sub>-Mediated Ring Expansions of Methylenecyclopropyl Amides and Imides
作者:Mark Lautens、Wooseok Han
DOI:10.1021/ja011110o
日期:2002.6.1
the reaction site in the dienolate with aryl aldimines and aldehydes as well as the size of the ring. Excellent divergent selectivity to five- vs. six-membered heterocycles is observed: alpha-alkylation/5-exo-tet cyclization (Z = NPh(2)) vs. gamma-alkylation/6-exo-trig cyclization (Z = 2-oxazolidone). Analogously, the reaction of the MCP imide with alkyl aldimines demonstrates the same selectivity by
MgI<sub>2</sub>-Mediated Ring Expansions of Secondary Methylenecyclopropyl Amides
作者:Mark Lautens、Wooseok Han、Jack Hung-Chang Liu
DOI:10.1021/ja028967l
日期:2003.4.1
Ring expansion of secondary methylenecyclopropyl amides in the presence of MgI2 was investigated. Various isomeric five-membered unsaturated lactams were obtained, depending on the character of the substituent Q. The amide group served as a nucleophile in ring closing as well as an activator for ring opening. In the presence of a variety of aryl aldimines or aldehydes, alkylative ring expansion occurred in a single step under mild and neutral conditions leading to gamma'-amino- or -hydroxy-alkylated pyrrol-2-ones. Also, it was shown that a 4-methylpyrrol-2-one could be transformed to a gamma-hydroxy-alkylated product by the use of a direct vinylogous aldol reaction.