Functionalized Chromans and Isochromans via a Diastereoselective Pd(0)-Catalyzed Carboiodination
摘要:
A diastereoselective approach to isochromans and chromans via Pd(0)-catalyzed carboiodination is reported. The transformations using this methodology display excellent yields and diastereoselectivities as well as broad functional group compatibility. The selectivity observed in these cyclizations, forming isochroman or chroman targets, is postulated to originate from the minimization of A(1,2) strain and axial axial interactions, respectively. This method has also been used to highlight the concept of reversible oxidative addition to carbon iodine bonds in polyiodinated substrates.
Rhodium-Catalyzed Synthesis of γ-Pyrones by Three Consecutive Redox-Aldol Reactions of Allylic Alcohols with α,β-Unsaturated Aldehydes
作者:Akio Mizuno、Hiroyuki Kusama、Nobuharu Iwasawa
DOI:10.1002/chem.201001068
日期:——
All together now! A unique RhI‐catalyzed reaction was developed to produce γ‐pyrones, which are 1,3,5‐triketone equivalents. This reaction was thought to proceed by three redox reactions of allylicalcohols, two intermolecular aldol reactions of α,β‐unsaturated aldehydes, and one intramolecular aldol reaction to afford 1,3‐cyclohexanediones, which were then converted into γ‐pyrones (see scheme; TMSOTf=trimethylsilyl
A Pd/Ca catalytic system to promote the unsymmetrical bis-allylation of malononitrile was developed by selecting conjugated dienes and allylic alcohols as allylic reagents. This catalytic system suppressed the competitive symmetrical bis-allylation process and guaranteed the desired unsymmetrical bis-allylation with high chemoselectivity. A wide range of conjugated dienes and allylic alcohols were