Chiral Gold Complex Catalyzed Cycloisomerization/Regio- and Enantioselective Nitroso-Diels–Alder Reaction of 1,6-Diyne Esters with Nitrosobenzenes

• Published in: ACS catalysis 2022-06, Vol.12 (12), p.7288-7299
• Main Authors: Yu, Lei, Li, Wenhai, Tapdara, Anyawan, Kyne, Sara Helen, Harode, Mandeep, Babaahmadi, Rasool, Ariafard, Alireza, Chan, Philip Wai Hong
• Format: Article
• Language: English
• ISSN: 2155-5435; 2155-5435
• DOI: 10.1021/acscatal.2c01680

An efficient chiral gold­(I) complex-catalyzed synthetic method that enables the cycloisomerization/regio- and enantioselective nitroso-Diels–Alder (NDA) reaction of 1,6-diyne esters with nitrosobenzenes is described. The sequential ring formation protocol offers access to a wide variety of 3,5,6,8a-tetrahydro-1H-benzo­[c]­[1,2]­oxazines as a single regioisomer in yields up to 99% and enantiomeric excess values of up to 99%. This is in contrast to the analogous NDA reactions of the cycloisomerized 1,6-diyne ester with nitrosoarenes in the absence of the chiral gold­(I) complex catalytic system, which were found to give the N,O-heterocyclic product with the opposite regiochemistry. Experimental and computational studies based on a postulated chiral dinuclear gold species containing two coordinated nitrosoarene molecules that undergoes an asynchronous concerted NDA reaction with the cycloisomerized 1,6-diyne ester provides insight into the observed product regio- and enantioselectivities.