An efficient Rh(II) carboxylate and Brønsted acid catalyzed direct π-extension of indoles to 4-substituted carbazoles is developed. The reaction involves a regioselective C-3 functionalization of indole by a rhodium enalcarbenoid and a Brønsted acid assisted cyclocondensation. In addition a twofold regioselective π-extension of pyrroles to 4,8-disubstituted carbazoles has also been developed. The utility of the methodology was demonstrated with the synthesis of analogues of an hepatitis C virus replication inhibitor and a secreted phospholipase A2 (sPLA2) inhibitor.
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,Oheterocyclic 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.
An efficient AgOTf catalyzed tandem intramolecular transannulation of ((2-alkynyl)aryl)cyclopropyl ketones leading to the 2,3-dihydronaphtho[1,2-b]furans has been developed. The reaction features a regioselective alkyne hydration, cyclopropylketone-2,3-dyhydrofuran rearrangement, and benzannulation. The methodology gives direct access to the tricyclic core structure of biologically important 2,3-dihydronaphtho[1,2-b]furan natural products.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.