Photochemical rearrangements of quinone monoketals
作者:Michael C. Pirrung、David S. Nunn
DOI:10.1016/0040-4020(96)00207-4
日期:1996.4
provides, after hydrolysis, β-carboxy-substituted cyclopentenones. With a substituent at the β-position of the quinone monoketal, rearrangement selectivity is modestly in favor of the more substituted alkene product. With a substituent at the α-position of the quinone monoketal, rearrangement selectivity is strongly in favor of the less substituted alkene product. Possible mechanistic reasoning to explain
An unexpected nucleophilic chlorination of a quinone monoketal while carrying out a pyrazolidine synthesis has led to a general preparation of multisubstituted phenols. The products are obtained in good to high yields under mild conditions. The bridged pyrazolidines that were the original targets are obtained in the presence of a protic solvent.
Chemoselectivity as a Delineator of Cuprate Structure in Catalytic 1,4-Addition of Diorganozinc Reagents to Michael Acceptors
作者:Matthias Welker、Simon Woodward、Luis F. Veiros、Maria José Calhorda
DOI:10.1002/chem.200903310
日期:2010.5.17
of this SR‐protected 1,4‐benzoquinone has been compared with the behavior of the analogous OR‐protected acetal in copper‐catalyzed additions of ZnMe2 by using chiral phosphoramidite ligands. The activation energy for 1,4‐methylation of the latter OR‐acetals with ZnMe2 (>95 % ee) has been determined for two CuX2 pre‐catalysts (X=OAc, 12.2 kcal mol−1; X=OTf, 6.7 kcal mol−1; Tf=triflate). The dithioacetal
Verfahren zur Herstellung von substituierten und unsubstituierten Cyclohexanonmonoketalen
申请人:Bayer CropScience AG
公开号:EP2055693A1
公开(公告)日:2009-05-06
Die vorliegende Erfindung betrifft ein Verfahren zur Herstellung und Isolierung bekannter substituierter und unsubstituierter 1,4-Cyclohexanonmonoketale der Formel (I).
Die Verbindungen (I) werden durch Hydrierung von Verbindungen der Formel (II) in Gegenwart eines geeigneten Metallkatalysators, gegebenenfalls eines Lösungsmittels und gegebenenfalls eines Additives hergestellt.
A wide range of cyclohexadienones has been synthesised in order to study their reactivity and their regio- and stereoselectivity with the enantiopure diene 1 under high-pressure conditions. Computational investigations were used to point out some parameters which affect the reactivity in this high chiral discrimination process. In addition, the resulting [4+2] cycloadducts allowed the preparation of new polyfunctional cyclohexenone derivatives.