Reaction of propenylbenzene derivatives and their analogs. I. Reaction of N,N-dibromobenzenesulfonamide with propenylbenzene derivatives.

Adachi, Taeko; Otsuki, Kazuo

doi:10.1248/cpb.24.2803

Cited by 5 publications

(1 citation statement)

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“…N - (3 - Methoxy - 4 - oxo - 2,5 - cyclohexadien - 1 - ylidene)benzenesulfonamide (2). A solution of ceric ammonium nitrate (14.67 g, 26.76 mmol) in H 2 O (40 mL) was added dropwise rapidly to a solution of N -(3,4-dimethoxyphenyl)benzenesulfonamide (2.63 g, 8.96 mmol) in acetonitrile (35 mL). The reaction mixture was stirred for 10 min and then diluted with CH 2 Cl 2 (100 mL).…”

Section: Methodsmentioning

confidence: 99%

Lewis Acid-Controlled Regioselectivity in Reactions of Styrenyl Systems with Benzoquinone Monoimides: New Regioselective Syntheses of Substituted 2-Aryl-2,3-dihydrobenzofurans, 2-Aryl-2,3-dihydroindoles, and 2-Arylindoles

1996

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Reactions of 4-(N-phenylsulfonyl)-2-alkoxy-1,4-benzoquinone monoimines 2-4 with electron-rich propenylbenzenes promoted by BF 3 yield 7-alkoxy-2-aryl-3-methyl-5-[(N-phenylsulfonyl)amino]-2,3-dihydrobenzofurans 5-7 nearly exclusively, whereas promotion of the reactions by Ti 4+ gives mixtures of the dihydrobenzofurans and their N-(phenylsulfonyl)-6-alkoxy-2-aryl-5-hydroxy-3-methyl-2,3-dihydroindole isomers 8-10, depending upon substituents present on the propenylbenzene. However, reactions promoted with excess Ti 4+ , as mixtures of TiCl 4 :Ti(OiPr) 4 , give the dihydroindoles as nearly the exclusive products. Evidence for a mechanism involving initial 5 + 2 cycloaddition of the Lewis acid-bound quinone monoimide with the propenylbenzene is found in reactions of styrenes 1f/g with monoimide 3 in which 7-aryl-3-hydroxy-6-methylbicyclo[3.2.1]oct-3-ene-2,8-diones 33 (5 + 2 adducts) are isolated. These reactions have been applied to stereoselective syntheses of pterocarpans bearing N-phenylsulfonyl groups, azapterocarpans and diazapterocarpans. In addition, DDQ oxidation of derivatives of several of the 2-aryl-2,3-dihydroindoles afford the corresponding 2-arylindoles in good yield. Finally, the experimental details of a general synthetic approach to 7-alkoxy-benzofuranoid neolignans, including (()-licarin B and eupomatenoids-1 and -12 are reported.

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Section: Methodsmentioning

confidence: 99%