Synthesis of Bicyclic Imidazoles via [2 + 3] Cycloaddition between Nitriles and Regioselectively Generated α-Imino Gold Carbene Intermediates
摘要:
The cyclic alpha-imino gold carbene intermediate B is most likely generated in situ via regioselective nitrene transfer from an azido group to a tethered terminal alkyne in the presence of a gold catalyst and at ambient temperature. This highly electrophilic intermediate can react with a weakly nucleophilic nitrile, which is used as the reaction solvent, to deliver a bicyclic imidazole rapidly in an overall bimolecular [2 + 2 + 1] cycloaddition and in mostly serviceable yield. The competing intramolecular Huisgen reaction, although likely also catalyzed by gold, is minimized by using AuCl3 as the catalyst.
Heterocyclic Aromatic Compounds Useful As Growth Hormone Secretagogues
申请人:Yu Guixue
公开号:US20090324625A1
公开(公告)日:2009-12-31
Novel heterocyclic aromatic compounds are provided that are useful in stimulating endogenous production or release of growth hormone, said compounds having the general structure of formula I
wherein R
1
, R
1
′, R
2
, R
3
, R
4
, Xa, Y, Z and n are as described herein. The compounds provided herein are useful in treating obesity, osteoporosis (improving bone density) and in improving muscle mass and muscle strength.