A library of chiral supramolecular ligands, named BenzaPhos, of straightforward preparation (two steps from commercially or readily available starting materials) and modular structure, was designed and synthesized. The ligands were screened in the search for new rhodium catalysts for the enantioselective hydrogenation of several benchmark and industrially relevant substrates. Once a series of hits
Synthesis of oxazines and thiazines by cyclodehydration of hydroxy amides and thioamides
作者:Peter Wipf、Gregory B. Hayes
DOI:10.1016/s0040-4020(98)00341-x
日期:1998.6
3-oxazines and -thiazines were obtained by cyclodehydration of hydroxy amides and thioamides with PEG-linked Burgess reagent or under Mitsunobu conditions. Yields were generally higher with polymer-Burgess reagent, but both conditions failed to cyclize δ- and ε-hydroxy amide precursors. In contrast, Burgess reagent was successful for the cyclodehydration of δ-hydroxy thioamide to give the expected