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
Enantioselective Phosphine-Catalyzed Formal [4+4] Annulation of α,β-Unsaturated Imines and Allene Ketones: Construction of Eight-Membered Rings
作者:Huanzhen Ni、Xiaodong Tang、Wenrui Zheng、Weijun Yao、Nisar Ullah、Yixin Lu
DOI:10.1002/anie.201707183
日期:2017.11.6
Magic eight “ring”: Under the catalysis of amino-acid-derived phosphines, the unprecedented [4+4] annulations between benzofuran/indole-derived α,β-unsaturated imines and allene ketones proceeded smoothly to afford azocines in excellent yields and with nearly perfect enantioselectivities. This work marks the first efficient asymmetric construction of optically enriched eight-membered rings by phosphine
Phosphine-mediated sequential annulations of allenyl ketone and isocyanide: a bicyclization strategy to access a furan-fused eight-membered ring and a spirocycle
Phosphine-mediated cascade annulations of allenyl ketone and isocyanide have been disclosed. Two molecular allenyl ketones work as different four-carbon synthons to form two rings, respectively, and thus enables the efficient synthesis of a furan-fused eight-membered ring and a spirocycle.
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
Allene Substitution-Controlled Switching of Dimerization to Cycloisomerization in the PdII-Catalyzed Reaction of Terminal α-Allenones
作者:Benito Alcaide、Pedro Almendros、Teresa Martínez del Campo
DOI:10.1002/ejoc.200700128
日期:2007.6
as catalyst, the cycloisomerization/dimerization ratio of α-allenones is controlled by the substitution of the allene compound: unsubstituted allenones mainly afford dimerization, whereas allenones bearing an internal substituent favor the formation of cycloisomerization products. Thus, for the first time the mode of reaction (cycloisomerization vs. dimerization) of α-allenones is substrate-directable