Nguyen Thien T
Institute of Research and Development, Duy Tan University, Da Nang 550000, Vietnam.
Faculty of Pharmacy, College of Medicine and Pharmacy, Duy Tan University, Da Nang 550000, Vietnam.
Org Biomol Chem. 2023 Jan 4;21(2):252-272. doi: 10.1039/d2ob01794f.
Asymmetric organocatalysis is a growing method for the synthesis of axially chiral tetrasubstituted allenes, the most challenging one among allene syntheses. In this method, chiral organocatalysts such as phase-transfer catalysts, peptides, disulfonimides, and binaphthyl/bispiro phosphoric acids have displayed remote control of regio- and stereoselectivity. Highly functionalized enantiopure allenes including those with an adjacent tertiary or quaternary stereocenter have been efficiently prepared with high levels of regio-, diastereo-, and enantioselectivity using this method. Several mechanistic pathways, including electrophilic addition to cumulenolate or zwitterionic enolate intermediates, alkynylogous Mukaiyama aldol reaction, nucleophilic addition to quinone methides, and dearomative addition to imino esters, were proposed. The method is necessary for providing access to axially chiral tetrasubstituted allenes, which can be utilized for the preparation of novel ligands, natural products, and organic materials, particularly those having complex structures. This review covers the enantioselective organocatalytic synthesis of these tetrasubstituted allenes and the mechanistic insights into the formation of the chiral axis up to July 2022.
不对称有机催化是合成轴手性四取代联烯的一种不断发展的方法，在联烯合成中这是最具挑战性的一类。在该方法中，手性有机催化剂，如相转移催化剂、肽、二磺酰亚胺和联萘/双螺磷酸，已展现出对区域和立体选择性的远程控制。利用这种方法，已高效制备出具有高区域、非对映和对映选择性的高度官能化对映体纯联烯，包括那些带有相邻叔碳或季碳立体中心的联烯。人们提出了几种机理途径，包括对累积烯醇盐或两性离子烯醇盐中间体的亲电加成、烯炔型 Mukaiyama 羟醛反应、对醌甲基化物的亲核加成以及对亚氨基酯的去芳构化加成。该方法对于获得轴手性四取代联烯是必要的，这些联烯可用于制备新型配体、天然产物和有机材料，特别是那些具有复杂结构的材料。本综述涵盖了截至2022年7月这些四取代联烯的对映选择性有机催化合成以及对手性轴形成的机理见解。
