Intramolecular Cyclization of Radicals Generated from α-Halomethylsulfonamides
作者:Silvana M. Leit、Leo A. Paquette
DOI:10.1021/jo991344e
日期:1999.12.1
A series of homologous alpha-sulfonamidyl radicals has been generated by reaction of alpha-halomethyl precursors with tri-n-butyltin hydride under AIBN catalysis. The intramolecular cyclization Capability of these highly reactive intermediates has been evaluated. Where possible, five-membered sultams are formed by 5-exo transition states. The longer C-SO2 and SO2-NR2 bonds have little demonstrable effect on this pathway. In larger systems, however, the 7-endo option predominates over the 6-exo alternative. A preparatively useful route to sultams has emerged from this investigation.
A Convenient Method for Removing All Highly-Colored Byproducts Generated during Olefin Metathesis Reactions
作者:Leo A. Paquette、Jeffrey D. Schloss、Ivan Efremov、Fabrizio Fabris、Fabrice Gallou、José Méndez-Andino、Jiong Yang
DOI:10.1021/ol000036w
日期:2000.5.1
Addition of a very modest amount of lead tetraacetate (1.50 equiv relative to the amount of Grubbs catalyst) to ring-closing metathesis reaction mixtures effectively removes all colored ruthenium and phosphine impurities to deliver colorless reaction products.
Direct Synthesis of Previously Inaccessible Bridgehead Azabicyclics by Intramolecular Cyclization of α-Sulfonamido and α-Sulfonimido Radicals
作者:Leo A. Paquette、Choon Sup Ra、Jeffrey D. Schloss、Silvana M. Leit、Judith C. Gallucci
DOI:10.1021/jo010216z
日期:2001.5.1
Syntheses of the first bridgehead sultams and the only known bridgehead disulfonimide are described. Both approaches capitalize on the electrophilicity of alpha-sulfonyl radicals and their propensity to undergo intramolecular ring closure. Where double bonds are concerned, 5-exo and 6-exo pathways operate preferentially as long as structural strain is not excessive. When the reaction center is a carbon-carbon