Indium(<scp>iii</scp>) triflate-catalysed [4 + 2] benzannulation reactions of o-alkynylbenzaldehydes with enolisable carbonyl compounds: selective synthesis of naphthyl ketones
作者:Karuppusamy Sakthivel、Kannupal Srinivasan
DOI:10.1039/c3ob41439f
日期:——
Indium(III) triflate is found to be an effective catalyst for the benzannulation reactions of o-alkynylbenzaldehydes with enolisable aldehydes, ketones, 1,3-diketones and β-keto esters. The reactions produce naphthyl ketones through ring opening of adducts arising from the inverse electron demand Diels–Alder reactions between in situ generated isochromenylium cations and enols. The main feature of the method is selective formation of naphthyl ketones in a highly regioselective manner without any decarbonylation.
Copper-Catalyzed [4+2]-Cycloadditions of Isoxazoles with 2-Alkynylbenzaldehydes To Access Distinct α-Carbonylnaphthalene Derivatives: C(3,4)- versus C(4,5)-Regioselectivity at Isoxazoles
作者:Sovan Sundar Giri、Rai-Shung Liu
DOI:10.1021/acscatal.9b02323
日期:2019.8.2
Cu(II)-catalyzed [4+2]-cycloadditions occur between Cu-benzopyryliums and substituted isoxazoles with the regioselectivity on the C(3,4)-carbons of isoxazoles. We postulate that a prior coordination of isoxazoles with Cu(OAc)(2) increases the pi-bond character of the C(3,4) carbons to become an effective 2 pi-donor. In this reaction sequence, 3,5-disubstituted isoxazoles yield alpha,gamma-dicarbonyl-naphthalenes whereas, beta-substituted isoxazoles deliver alpha,gamma-dicarbonyl-beta-aminonaphthalenes. For unsubstituted isoxazole, its cycloaddition chemoselectivity is switched to the C(4,5)-addition regioselectivity to yield alpha-carbonyl-gamma-cyanonaphthalene derivatives.