Metal-Free Decarboxylative Cyclization/Ring Expansion: Construction of Five-, Six-, and Seven-Membered Heterocycles from 2-Alkynyl Benzaldehydes and Cyclic Amino Acids
A one pot synthesis of 1H‐benzo[g]indoles, tetrahydrobenzo[h]quinolines, and naphtho[1,2‐b]azepines from 2‐alkynyl benzaldehydes and cyclic amino acids is reported. The salient feature of the strategy involves formation of three new bonds (one CN and two CC bonds) by a metal‐free decarboxylation/cyclization/one‐carbon ring expansion sequence in one pot.
Asymmetric Cascade Annulation Based on Enantioselective Oxa-Diels–Alder Cycloaddition of in Situ Generated Isochromenyliums by Cooperative Binary Catalysis of Pd(OAc)<sub>2</sub> and (<i>S</i>)-Trip
作者:Shu-Yan Yu、Hao Zhang、Yang Gao、Lei Mo、Shaozhong Wang、Zhu-Jun Yao
DOI:10.1021/ja405764p
日期:2013.7.31
An asymmetric cascade annulation between 2-hydroxystyrenes and 2-alkynylbenaldehyes or 1-(2-alkynylphenyl)ketones has been established with good to excellent enantioselectivities (up to >99.5% ee), on the basis of an enantioselective oxa-Diels-Alder cycloaddition of in situ generated metallo-isochromenylium intermediates, by cooperative binary catalysis of Pd(OAc)(2) and (S)-Trip. The developed methodology is workable for a broad spectrum of substrates and shows great efficiency in establishing dense multiple chiral centers including quaternary carbons of variable bridged ring systems. The mechanism study suggests that (S)-Trip plays multiple roles in assembling the reactants and controlling the stereoselectivity.