trans-2-Aryl-3-nitro-cyclopropane-1,1-dicarboxylates, upon treatment with BF3·OEt2, undergo ring-opening rearrangement and the Nef reaction to give aroylmethylidene malonates. The products are found to be potential precursors for heterocycles, such as imidazoles, quinoxalines, and benzo[1,4]thiazines.

trans-2-Aryl-3-nitro-cyclopropane-1,1-dicarboxylates when reacted with nitriles in the presence of tin(IV) chloride afford 2,4,5-trisubstituted oxazoles in good to excellent yields. The reactions take place through in situ generation of aroylmethylidene malonates from the cyclopropanes, followed by conjugate addition of nitriles to the malonates to form nitrilium ion intermediates and subsequent cyclisation.

In the presence of indium triflate, o-alkynylbenzaldehydes form isochromenylium cations that react with enones such as chalcones and diarylidineacetones to give 1,2-dihydronaphthalenes in moderate to good yields. The reaction proceeds via a rare type of Diels-Alder reaction in which both the diene (isochromenylium cation) and the dienophile (enone) are electron deficient.

The indium(III) triflate-catalyzed reaction of aza-Michael adducts of chalcones with aromatic amines has been investigated. The Michael adducts derived from substituted anilines and chalcones underwent retro-Michael addition to give the original starting materials, whereas the adducts derived from 1-naphthylamines and chalcones afforded quinolines. A six-membered cyclic transition state has been proposed to explain the retro-Michael addition, while a Povarov mechanism has been put forward to explain the quinoline formation.

A two-step synthesis of 2,3-disubstituted thiophenes from trans-2-aryl-3-nitrocyclopropane-1,1dicarboxylates and 1,4-dithiane-2,5-diol is described. Ar NO 2 CO 2 Et EtO 2 C 1) BF 3 OEt 2 , CH 2 Cl 2 , rt S CO 2 Et EtO 2 C OH Ar O 25-87% S S HO OH 2) Et 3 N p-TsOH PhMe, 90 C°S EtO 2 C O Ar 61-88%were aromatised to target thiophenes using p-toluenesulfonic acid. To prove the synthetic utility of the synthesised thiophenes, one of the thiophenes was transformed into a bis(thiophene) by a palladium-mediated homocoupling. Further scope of the methodology is under investigation.