Chiral Silver Phosphate Catalyzed Transformation of ortho‐Alkynylaryl Ketones into 1H‐Isochromene Derivatives through an Intramolecular‐Cyclization/Enantioselective‐Reduction Sequence

Abstract

The transformation of ortho-alkynylaryl ketones through a cyclization/enantioselective-reduction sequence in the presence of a chiral silver phosphate catalyst afforded 1H-isochromene derivatives in high yield with fairly good to high enantioselectivity. An asymmetric synthesis of the 9-oxabicyclo[3.3.1]nona-2,6-diene framework, which has been found in some biologically active molecules, is presented as a demonstration of the synthetic utility of this method.

Silver-catalysed reactions of alkynes: recent advances

“…294 In recent years, chiral counterion-induced enantioselective transformations, i.e., asymmetric counterion-directed catalysis (ACDC) have emerged as powerful tools in asymmetric synthesis. 296 This reaction proceeded through a tandem cyclization/enantioselective-reduction reaction pathway with a chiral silver phosphate catalyst 407 as well as a Hantzsch ester 408 as the reductant. 296 This reaction proceeded through a tandem cyclization/enantioselective-reduction reaction pathway with a chiral silver phosphate catalyst 407 as well as a Hantzsch ester 408 as the reductant.…”

Iodine‐Mediated Cyclization of ortho‐Alkynylaryl Ketones for the Synthesis of Indenone Derivatives

“…(4‐Methoxyphenyl)[2‐(phenylethynyl)phenyl]methanone (1): Yellow oil (463.5 mg, 99 %). IR (neat) ν̃ = 2940, 1651, 1580, 1412, 1330, 1122 cm –1 .…”

Enantioselective Copper-Catalyzed Alkynylation of Benzopyranyl Oxocarbenium Ions

“…7 Subsequently, Terada and Floreancig showed that phosphoric acid catalysts can also be used to catalytically generate chiral oxocarbenium ion electrophiles, which undergo enantioselective attack by hydride or allyl nucleophiles, respectively. 8 In a distinct strategy, Schaus has demonstrated the complementary approach of catalytic generation of a chiral nucleophile via tartarate-derived diol-catalysis of vinyl and aryl boronate esters. 9 Rueping, Lou and Liu, and Cozzi have also shown that chiral enamine nucleophiles, catalytically generated from amine catalysts and aldehydes, add to oxocarbenium ions with high enantioselectivities.…”