The direct sulfenylation of indoles with aromatic thiols has been accomplished in the presence of 20 mol% of FeCl 3 in refluxing acetonitrile to produce 3-arylthioindoles in relatively good to excellent yields and with high selectivity. This method works even with 2-unsubstituted indoles.
An efficient organocatalytic vinylogous Michael addition-triggered quadruple cascade reaction resulting in fused spiroxindoles bearing multiple quaternary stereocenters is demonstrated from β-trifluoroacetylarylidene indanediones and 3-alkylideneoxindoles.
α-Halohydrazones/ketoximes are transformed into trisubstituted pyrazoles/disubstituted isoxazoles by treatment with phosphine, acyl chloride, and a base. Mechanistic investigations revealed the in situ formation of azo/nitroso olefin intermediates which underwent a tandem phospha-Michael/N-or O-acylation/intramolecular Wittig reaction to afford the heteroarenes in moderate to good yields. Further, proper functionalization of α-haloketoximes and a change of conditions allowed the chemoselective synthesis of chromenone-oximes as well as rearranged isoxazoles, thereby realizing a diversity-oriented synthesis.
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