Friedel–Crafts alkylations of electron-rich aromatics with 3-hydroxy-2-oxindoles: scope and limitations
作者:Lakshmana K. Kinthada、Santanu Ghosh、K. Naresh Babu、Mohd. Sharique、Soumava Biswas、Alakesh Bisai
DOI:10.1039/c4ob01264j
日期:——
A Lewis acid-catalyzed nucleophilic addition of electron rich aromatics with 3-hydroxy-2-oxindoles 5 was developed. The reaction is believed to proceed through the 2H-indol-2-one ring system 9, which eventually reacts with various electron-rich aromatics to afford a variety of 2-oxindoles with an all-carbon quaternary center at the pseudobenzylic position (4, 8, 13, and 16) in high yields. The methodology provides an expeditious route to the tetracyclic core (3) of diazonamide (1), and azonazine (2) as well as the tricyclic core of asperazine (6a), idiospermuline (6b), and calycosidine (6c) viz. C(3a)-arylpyrroloindolines 7 having an all-carbon quaternary center on further synthetic elaboration.
Lewis acid-catalyzed Friedel–Crafts alkylations of 3-hydroxy-2-oxindole: an efficient approach to the core structure of azonazine
作者:Santanu Ghosh、Lakshmana K. Kinthada、Subhajit Bhunia、Alakesh Bisai
DOI:10.1039/c2cc35283d
日期:——
A Lewis acid catalyzed FriedelâCrafts reaction of electron rich aromatics with 3-alkyl-3-hydroxy-2-oxindole (5) has been developed. The methodology provides a straightforward access to the core of azonazine (2) sharing an all-carbon quaternary stereocenter at the tetracyclic ring junction.
A new method has been developed for constructing vicinal quaternary stereocenters with an oxindole–butanolide hybrid framework through asymmetric vinylogous addition of a siloxyfuran to an indol-2-one in the presence of a readily available N,N′-dioxide–Ni(OTf)2 complex catalyst. Various oxindole–lactones were obtained in up to 98% yield with >19:1 dr and 97% ee under mild reaction conditions. A possible
开发了一种新方法,通过在容易获得的N , N ' -二氧化物-Ni(OTf)存在下,将甲硅氧呋喃不对称插烯加成到吲哚-2-酮上,从而构建具有羟吲哚-丁内酯杂化骨架的邻位季立体中心2络合物催化剂。在温和的反应条件下,以 >19:1 dr 和 97% ee 获得了高达 98% 的收率和 97% ee 的各种羟吲哚内酯。提出了一种可能的过渡态模型来解释不对称感应的起源。
Enantioselective Synthesis of 3‐Substituted 3‐Amino‐2‐oxindoles by Amination with Anilines
AbstractA chiral N,N′‐dioxide‐nickel(II) complex‐catalyzed asymmetric amination of 3‐bromo‐3‐substituted oxindoles with anilines has been developed. A series of alkyl or aryl 3‐amino‐indolinones with quaternary stereocenters were obtained in high yields with excellent ee values in one step (up to 99 % yield, up to 96 % ee). The method provided a ready route to optically active intermediates of 3‐amino‐2‐oxindole‐based bioactive compounds. Moreover, a possible transition‐state model is proposed so as to elucidate the origin of the chirality based on the X‐ray crystal structure of the catalyst and the adduct.
Chatterjee, Asima; Pandit, Uttam Kumar; Sarkar, Suvra, Journal of the Indian Chemical Society, 1982, vol. 59, # 4, p. 523 - 525
作者:Chatterjee, Asima、Pandit, Uttam Kumar、Sarkar, Suvra、Shoolery, J. N.