Halogen-Mediated Cascade Cyclization Reaction of Aryldiynes to Indeno[1,2-c]chromene Derivatives.

The halogen-mediated cyclization reaction of aryldiynes to produce halogenated indeno[1,2-c]chromene derivatives is described. Treatment of aryldiynes 1 with one equivalent of iodine gave iodinated indeno[1,2-c]chromenes 3 in good chemical yields. When two equivalents of iodine were employed into the reaction mixture, dimer 9 was obtained as the major products. On the other hand, reaction of two equivalents of CuBr2 with compounds 1 gave the brominated indeno[1,2-c]chromenes 4. The DFT calculation of the iodine-mediated cyclization reactions for molecules containing methoxy, carboxy, amino, and sulfide substituents were carried out in order to understand how the substituent affects the cyclization pathway.

Base-Mediated Cyclization Reaction of 2-(5-Hydroxy-1-pentynyl)benzonitriles to 4-Amino-2,3-dihydronaphtho[2,3-b]furanes and Synthesis of Furanonaphthoquinones.

An efficient transformation of 2-(5-hydroxy-1-pentynyl)benzonitriles 5 to furanonaphthoquinones 11 is presented. Treatment of 5 with 1.5 equiv of NaOMe in DMSO at 140 °C for 0.5 h gave 6 in good yields. Conversion of 6 to 11 was carried out by oxidation of 6 with Fremy's salt and KH2PO4 in acetone and water, followed by dehydrogenation using palladium on charcoal in diphenylether at reflux temperature.

Transition metal-catalyzed cascade cyclization of aryldiynes to halogenated benzo[b]naphtho[2,1-d]thiophene derivatives.

Treatment of 2-(2-(2-(2-substituted ethynyl)phenyl)ethynyl)thioanisoles (1) with 5 mol % of Ph3PAuCl/AgSbF6 and 2 equiv of NIS at refluxing CH2Cl2 gave iodo-substituted benzo[b]naphtho[2,1-d]thiophene (6) in good yields. Chloro- and bromo-substituted benzo[b]naphtho[2,1-d]thiophene derivatives (8 and 9) were also generated by treating compound 1 with 5 mol % of PdX2 and 3 equiv of CuX2 at refluxing THF.

Tupichinins B-D, three new spirostanol saponins from Tupistra chinensis rhizomes.

Three new spirostanol saponins were isolated from the EtOAc fraction of methanol extract from Tupistra chinensis rhizomes. Based on the detailed analysis of their 1D and 2D NMR spectra and chemical evidence, their structures were determined as 1ß-O-acetyl-spirost-5,25(27)-dien-3α-yl-O-ß-D-glucopyranoside (1), (25S)-1ß,2ß,5ß-trihydroxy-spirostane-3ß-yl-O-ß-D-glucopyranoside (2) and (25S)-1ß,2ß-dihydroxy-5ß-spirostane-3ß-yl-O-ß-D-xylopyranoside (3), respectively.

Iodine-mediated cascade cyclization of enediynes to iodinated benzo[a]carbazoles.

Treatment of N,N-dimethyl 2-[2-(2-ethynylphenyl)ethynyl]anilines (1) with 1.2 equiv of iodine in CH(2)Cl(2) gave benzo[a]carbazoles (2) in good yields. Mechanistic studies showed this reaction must go through the haloindole (3) followed by iodonium ion catalyzed atom-transfer cyclization reaction to give the benzo[a]carbazoles.

Synthetic development and mechanistic study on Pd(II)-catalyzed cyclization of enediynes to benzo[a]carbazoles.

Treatment of N,N-dimethyl 2-[2-(2-ethynylphenyl)ethynyl]anilines (1) with 10 mol % of palladium chloride and 2 equiv of cupric chloride in refluxing THF gave benzo[a]carbazoles (6) in good yields. A mechanistic study showed that this reaction must proceed through formation of haloindole (7) followed by a palladium(II)-catalyzed atom transfer cyclization reaction to give the benzo[a]carbazoles.

Palladium-catalyzed annulation of 2-(1-alkynyl)biphenyls with aryl iodides to disubstituted methylidenefluorenes.

The palladium-catalyzed annulation reaction of 2-(1-alkynyl)biphenyls (1) with aryl iodides has been developed to prepare a variety of diarylmethylidenefluorenes (2). This method tolerates various functional groups in aryl iodide, such as OCH(3), CH(3), Cl, Br, Cf(3), and NO(2). All proceed in good yield with the exception of 4-iodonitrobenzene.