Kinetic Resolution in 1,3-Dipolar Cycloaddition of Tartaric Acid-Derived Nitrones to 2,3-Dihydro-1-phenyl-1H-phospholes. An Enantioselective Approach to the 2,2'-Coupled Pyrrolidine-Phospholane Ring System
作者:Alberto Brandi、Stefano Cicchi、Andrea Goti、Marek Koprowski、K. Michal Pietrusiewicz
DOI:10.1021/jo00085a019
日期:1994.3
Enantiomerically pure five-membered ring nitrones derived from L-tartaric acid via C2-symmetric O,O'-protected 3,4-dihydroxy pyrrolidines undergo highly regio- and stereoselective cycloaddition reactions with racemic 2,3-dihydro-1-phenyl-1H-phosphole 1-oxide and 1-sulfide. In all cases formation of only two diastereomeric cycloadducts is observed and their ratio (up to 10:1) is dependent on the size of the protecting groups in the nitrone and on the extent of conversion. The tricyclic cycloadducts feature 2,2'-connection of pyrrolidine and phospholane rings and six contiguous stereogenic centers of which three are created and the one at phosphorus is kinetically resolved during the cycloaddition process. It is established that in the studied kinetic resolutions the stereoselectivity factor 8 = k(S)/k(R) exceeds the value of 10 (up to 14) in the most favorable cases. In a properly tuned reaction both the diastereomeric cycloadducts and the enantiomerically enriched dihydrophosphole derivative can be simultaneously obtained in satisfactory chemical and optical yields.
Pietrusiewicz, K. Michal, Phosphorus, Sulfur and Silicon and the Related Elements, 1996, vol. 109, # 1-4, p. 573 - 576
作者:Pietrusiewicz, K. Michal
DOI:——
日期:——
Asymmetric and Doubly Asymmetric 1,3-Dipolar Cycloadditons in the Synthesis of Enantiopure Organophosphorus Compounds
[EN] METHODS FOR PREPARING POWDER COATING COMPOSITIONS<br/>[FR] PROCÉDÉS DE PRÉPARATION DE COMPOSITIONS DE REVÊTEMENT PULVÉRULENTES
申请人:PPG IND OHIO INC
公开号:WO2018048709A1
公开(公告)日:2018-03-15
Disclosed is a method for preparing powder coating compositions. The method includes mixing in an aqueous medium a carboxylic acid functional polymer having a high glass transition temperature, with a polycarbodiimide having a high glass transition temperature, drying the mixture, and grinding the resulting solid particles to obtain a powder.