Titanium-Catalyzed, One-Pot Synthesis of 2-Amino-3-cyano- pyridines
摘要:
AbstractEarth‐abundant and inexpensive titanium can catalyze alkyne iminoamination, which generates tautomers of 1,3‐diimines. Upon treatment with base (DBU) and malononitrile, the multicomponent coupling product is converted to 2‐amino‐3‐cyanopyridines in a one‐pot procedure in good to modest yields. There is substantial control of regioselectivity for the substituents on the pyridine ring and on the 2‐amino group. Several studies were done that provide significant evidence for a Dimroth rearrangement mechanism for 2‐aminopyridine formation, including isolation of a 2‐imino‐1,2‐dihydropyridine intermediate that undergoes rearrangement under the reaction conditions.magnified image
Regioselective conversion of alkynes to 4-substituted and 3,4-disubstituted isoxazoles using titanium-catalyzed multicomponent coupling reactions
作者:Amila A. Dissanayake、Aaron L. Odom
DOI:10.1016/j.tet.2011.11.043
日期:2012.1
Conditions have been developed for the regioselective synthesis of 4-substituted isoxazoles from terminal alkynes and 3,4-disubstituted isoxazoles from internal alkynes. The methodology involves a one-pot titanium-catalyzedmulticomponentcouplingreaction followed by simple hydroxylamine hydrochloride addition.