Oppolzer-Type Intramolecular Diels–Alder Cycloadditions via Isomerizations of Allenamides
摘要:
A new approach to Oppolzer's Intramolecular Dlels-Alder cycloaddition (IMDA) through gamma-isomerlzation of readily available N-tethered allenamides is described. These IMDA reactions are carried out in tandem with the allenamide isomerization or 1,3-H shift, leading to complex nitrogen heterocycles in a highly stereoselective manner.
Alloc=allyloxycarbonyl, Boc=tert‐butyloxycarbonyl). These reactions are the first examples of the formation of medium‐sized rings by the intramolecular cyclopropanation of an alkene with a donor‐substituted rhodium carbenoid, which is not generated from a diazo compound.
1,6-Dipolar cycloadditions represent a valuable strategy for the rapid construction of medium-sized rings. Herein, we describe the concept for the design of 1,6-dipoles that bypasses the regioselectivity. Through the introduction of an amino group into Morita–Baylis–Hillman (MBH) carbonates, unprecedented [6 + 2] dipolarcycloadditions were accurately developed with Cs2CO3, efficiently delivering a
DABCO catalyzed [4+2] annulations of Morita–Baylis–Hillman carbonates with isocyanates
作者:Wei Cai、Yiming Zhou、Yanlin He、You Huang
DOI:10.1039/d1cc03502a
日期:——
A highly concise method for 1,4-diazabicyclo[2.2.2]octane (DABCO) catalyzed [4+2] annulations of o-amino-acylation of aryl MBH carbonates with isocyanates has been developed. For the first time, MBH carbonates served as 1,4-dipoles, providing functionalized 3,4-dihydroquinazolinones in mild conditions with good to excellent yields. The density functional theory calculations of the mechanism supports
A Convenient Allenoate-Based Synthesis of 2-Quinolin-2-yl Malonates and β-Ketoesters
作者:Philipp Selig、William Raven
DOI:10.1021/ol502554e
日期:2014.10.3
N-protected o-aminobenzaldehydes smoothly react with alpha,gamma- dialkylallenoates under Bronsted basic conditions to yield 2,3-disubstituted quinolines. This three step reaction cascade of Michael addition, aldol condensation, adn 1,3 N -> C rearrangement uses the complete protecting group as a building block in a highly efficient C,C-bond formation of a new all carbon quaternary center. Carbamate protected substrates (N-Boc, N-Cbz, N-Alloc) thus give 2-quinolin-2-yl-malonates, while amide protected substres (NAc,NBz) afford 2 quinolin 2-yl-beta-ketoesters in high yields.