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Abstract: An efficient and practical method for construction of 2-arylbenzo[b]furans from 2-methoxychalcone epoxides has been reported. Catalyzed by 2 mol % of BF3·Et2O, 2-methoxychalcone epoxides went through the Meerwein rearrangement, followed by deformylation in one-pot to successfully afforded 2-methoxydeoxybenzoins. Afterward, 2-arylbenzo[b]furans were obtained in high yields (87%–100%) via intermolecular cyclodehydration of 2-methoxydeoxybenzoins with 48% HBr. By utilization of this approach, the natural product stemofuran A and the key intermediate of eupomatenoid 6 have been synthesized conveniently. [Copyright &y& Elsevier]

An efficient and highly regioselective synthetic method has been developed for the preparation of novel cyclobutene-containing spiro[2.3]hexenes fused with six or seven-membered carbo- or hetero-cycles in good to excellent yields following a thermal induced intramolecular [2+2] cycloaddition of alkynone-vinylidenecyclopropanes or a sequential oxidation/thermal induced intramolecular [2+2] cycloaddition process of propynol-vinylidenecyclopropanes under metal-free conditions. [ABSTRACT FROM AUTHOR]

Abstract: One-pot thermal-induced [3+2] cycloaddition/silica gel-promoted fragmentation sequence between isatin ketonitrones and electron-deficient alkynes affords spiro[indoline]oxindoles in moderate to excellent yields along with good diastereoselectivities. The detailed mechanism of silica gel-promoted fragmentation has been clarified by experiment and DFT calculations. [Copyright &y& Elsevier]

Abstract: Cyclization reactions of ethyl 2-(2-hydroxyaryl)-2-oxoacetates with ethyl 2,3-butadienoate and allenylsulfone proceeded smoothly in the presence of tertiary phosphine and sodium p-toluenesulfinate (SPTS) to give the corresponding quaternary carbon centered chromans in moderate to good yields under mild conditions, which provides an alternative efficient approach for the synthesis of biologically active chroman products. [Copyright &y& Elsevier]

Abstract: In this paper, we reported that phosphorus-containing Lewis bases catalyzed [4+2] cyclization of N-protected isatin derived electron-deficient alkenes with but-3-yn-2-one could proceed smoothly to give the corresponding dihydropyrano[2,3-b]indoles in good to excellent yields under mild conditions. The substrate scope has been carefully examined and the plausible reaction mechanism has been also proposed. [Copyright &y& Elsevier]

Abstract: The reaction of isoquinoline and allenoate with activated ketone resulted in a novel three component reaction, affording [1,3]oxazino[2,3-a]isoquinoline derivatives in moderate yields along with moderate diastereoselectivities via 1,4-dipolar cycloaddition. It was also found that when isatins were used as substrates, the regioselectivity of cycloadducts was different from those using ethyl trifluoropyruvate as substrate. [Copyright &y& Elsevier]

The first conjugate addition of α-isocyanoacetates with in situ generated azoalkenes from α-halogeno hydrazones in the presence of Cs 2 CO 3 has been developed. The reaction condition was suitable to various α-aryl substituted isocyanoacetates as well as aryl and alkyl-substituted α-halogeno hydrazones, affording the corresponding products in good to high yields. The adducts can be easily transformed into biologically attractive 1,4-dihydropyrimidine derivatives via an intramolecular cyclization by treating with AgOAc. The one-pot conjugate addition/intramolecular cyclization has also been investigated to furnish the formal [3 + 3] cycloadduct, 1,4-dihydropyrimidine derivatives. [Display omitted] [ABSTRACT FROM AUTHOR]