An efficient cobalt(III)-catalyzed intramolecular cross-dehydrogenative C-H/N-H coupling of ortho-alkenylanilines has been developed utilizing O as a terminal oxidant. The developed reaction tolerates various reactive functional groups and allows the synthesis of diverse indole derivatives in good to excellent yields. The method was successfully extended to the synthesis of benzofurans through the intramolecular cross-dehydrogenative C-H/O-H coupling of ortho-alkenylphenols.
An efficient and novel rhodium-catalyzed transannulation of N-sulfonyl-1,2,3-triazoles with in situ generated o-quinone methides ( o-QMs) from 2-hydroxybenzyl alcohols has been achieved for the synthesis of substituted benzopyrans in good yields. The developed reaction involves nucleophilic attack of o-QM to α-imino rhodium carbenoid to generate a carbonyl ylide followed by 6π-electrocyclization and isomerization. Furthermore, the utility of the methodology was demonstrated in the one-pot synthesis and construction of polyheteroaromatics.
An efficient diastereoselective rhodium catalyzed synthesis of indolines possessing two contiguous tetrasubstituted carbon centers has been achieved with good to excellent yields using ortho-vinylanilines and iminocarbenes derived from N-sulfonyl-1,2,3-triazoles.
An efficient rhodium-catalyzed unprecedented oxa-[2,3]-sigmatropic
rearrangement of sulfur ylide derived from α-thioesters/ketones
and diazo carbonyl compounds has been accomplished for the synthesis
of various sulfur-tethered vinylogous carbonates in good to excellent
yields. Important features of the developed reaction include wide
functional group tolerance, excellent chemo- and regioselectivity,
and efficient rearrangement involving the carbonyl motif. The present
reaction also equally works well with α-selenoesters for the
synthesis of seleno-containing vinylogous carbonates.
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