A one-pot, tandem process has been developed for the synthesis of a library of tetrazoles from aryl isothiocyanates. Condensation of aryl isothiocyanates with ammonia, and aryl amines (R-NH(2)) provided mono, 1,3-disubstituted symmetrical and unsymmetrical thioureas, which on desulfurization with molecular iodine (I(2)) led to formation of the corresponding heterocumulene (cyanamides or carbodiimides). The in situ generated heterocumulene on subsequent treatment with sodium azide at room temperature gave corresponding tetrazoles. The product regioselectivity for unsymmetrical 1,3-disubstituted thioureas was found to be correlated with the basicities (pK(a)'s) of the parent amines attached to the thiourea. Aryl-sec-alkyl unsymmetrical thioureas gave thioamido guanidino products rather than the 5-aminotetrazoles produced by HgCl(2) mediation of the reaction. Bis-thioureas derived from aryl isothiocyanates and hydrazine gave thiadiazoles exclusively.

CuO nanoparticle catalyzed synthesis of 2,3-disubstituted quinazolinones has been accomplished from 2-halobenzamides and (aryl)methanamines under an air atmosphere. This synthesis of the N-heterocycle involves a sequential Ullmann coupling [between 2halobenzamide and (aryl)methanamine], oxidation of the in situ generated secondary amine to imine. This is then followed by an intramolecular nucleophilic attack of the amidic N−H on to the imine carbon (C−N bond formation) resulting in the synthesis of 2,3disubstituted quinazolinones. The recyclability of the catalyst and tolerance of a wide range of functional groups makes this method efficient and cost-effective.

C-3 alkylation of coumarins has been accomplished using cycloalkanes or alkylbenzenes in the presence of di-tert-butylperoxide (DTBP) and Fe(III) catalyst. Under metal free conditions and just by switching the oxidant from DTBP to TBHP, an exclusive C-4 cycloalkylation-C-3 peroxidation reaction takes place. During C-3 alkylation, the C-C bond formation occurs at the expense of an existing C-C bond, while the C-4 alkylation is associated with the formation of new C-C and C-O bonds.

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By using alkylbenzenes as aroyl surrogates, copper(II) catalyzed chemoselective O-aroylations of 1,3-dicarbonyl compounds and phenolic -OH ortho to carbonyl (-CHO, -COR) groups have been achieved. A dual mechanism operating in tandem for these transformations has been supported by a crossover experiment.