Highly Enantioselective Synthesis of 3,4-Dihydropyrans through a Phosphine-Catalyzed [4+2] Annulation of Allenones and β,γ-Unsaturated α-Keto Esters
作者:Weijun Yao、Xiaowei Dou、Yixin Lu
DOI:10.1021/ja5109358
日期:2015.1.14
A phosphine-catalyzed novel [4+2] annulation process was devised employing allene ketones as C2 synthons and β,γ-unsaturated α-keto esters as C4 synthons. In the presence of an L-threonine-derived bifunctional phosphine, 3,4-dihydropyrans were obtained in high yields and with virtually perfect enantioselectivities. The synthetic value of the dihydropyran motif was demonstrated by a concise preparation
Baylis–Hillman reactions of N-tosyl aldimines and aryl aldehydes with 3-methylpenta-3,4-dien-2-one
作者:Gui-Ling Zhao、Min Shi
DOI:10.1039/b510572b
日期:——
The attempted BaylisâHillman reactions of N-tosyl aldimines and aryl aldehydes with 3-methylpenta-3,4-dien-2-one gave the corresponding BaylisâHillman adducts 3 and 6 in moderate to good yields in the presence of DMAP in DMSO, respectively. In the case of the aza-BaylisâHillman reactions of N-tosyl aldimines with 3-methylpenta-3,4-dien-2-one catalyzed by PBu3, the corresponding aza-BaylisâHillman derivatives 4 and 5 were formed at the same time.
Synthesis of Functionalized 2<i>H</i>-1-Benzopyrans by DBU-Catalyzed Reactions of Salicylic Aldehydes with Allenic Ketones and Esters
作者:Gui-Ling Zhao、Yong-Ling Shi、Min Shi
DOI:10.1021/ol051920v
日期:2005.9.1
[reaction: see text] DBU-catalyzed reactions of salicylicaldehydes with 3-methylpenta-3,4-dien-2-one, 3-benzylpenta-3,4-dien-2-one, or ethyl 2-methylbuta-2,3-dienoate gave the corresponding functionalized 2H-1-chromenes in good to excellent yields and good diastereoselectivities in some cases in DMSO, respectively.
Potassium Carbonate-Catalyzed Reactions of Salicylic Aldehydes with Allenic Ketones and Esters: an Effective Way to Synthesize Functionalized 2H-Chromenes
Potassiumcarbonate-catalyzedreactions of salicylicaldehydes with 3-methylpenta-3,4-dien-2-one, 3-benzylpenta-3,4-dien-2-one or ethyl 2-methylbuta-2,3-dienoate gave the corresponding functionalized 2H-1-chromenes in good to excellent yields and good stereoselectivities in some cases in DMSO at 120 °C within 1 h, respectively.
碳酸钾催化的水杨醛与3-甲基戊-3,4-二烯-2-酮,3-苄基戊-3,4-二烯-2-酮或2-甲基丁-2,3-二烯乙基乙酯的反应在某些情况下,在DMSO中于120°C下1 h内,分别以良好至极好的收率和良好的立体选择性对2 H -1-色烯进行了功能化。
Ferrocene Derived Bifunctional Phosphine-Catalyzed Asymmetric Oxa-[4+2] Cycloaddition of α-Substituted Allenones with Enones
作者:Huamin Wang、Weike Lu、Junliang Zhang
DOI:10.1002/chem.201703368
日期:2017.10.4
An efficient ferrocene‐derived bifunctional phosphine‐catalyzed enantioselective oxa‐[4+2] cycloaddition of α‐substituted allenones with a broad range of enones is investigated for the preparation of stereodefined dihydropyrans in good to excellent yields (up to 99 %) and excellent enantioselectivity (up to 99 % ee). Furthermore, a series of valuable chiral polyheterocyclic frameworks can be efficiently