1981
DOI: 10.1016/s0040-4039(01)93272-1
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Regioselectivities of Diels-Alder cycloadditions to methoxy-substituted quinones

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Cited by 24 publications
(7 citation statements)
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“…In order to prepare HBADs analogous to 36 and 37 but with the opposite regiochemistry in the aromatic ring portion, the regioselectivity of the Diels-Alder reaction required alteration. Tegmo-Larsson et al 15 reported that 2,5-dimethoxybenzoquinone underwent a Diels-Alder reaction with 22 to give an adduct which, upon loss of MeOH, gave the 5,8-dihydronaphthalene with the methyl group in the desired 5-position. In our hands, this reaction proceeded slowly and was impractical for our needs.…”
Section: Aqueous Acid Hydrolysis Gave Hbads 19-21mentioning
confidence: 99%
See 1 more Smart Citation
“…In order to prepare HBADs analogous to 36 and 37 but with the opposite regiochemistry in the aromatic ring portion, the regioselectivity of the Diels-Alder reaction required alteration. Tegmo-Larsson et al 15 reported that 2,5-dimethoxybenzoquinone underwent a Diels-Alder reaction with 22 to give an adduct which, upon loss of MeOH, gave the 5,8-dihydronaphthalene with the methyl group in the desired 5-position. In our hands, this reaction proceeded slowly and was impractical for our needs.…”
Section: Aqueous Acid Hydrolysis Gave Hbads 19-21mentioning
confidence: 99%
“…The ice bath was removed, and the reaction mixture was allowed to stir at 25 °C for 20 h. NBS (1.03 g, 5.80 mmol) was added in one portion, and the reaction mixture was allowed to stir at 25 °C for 48 h. A second portion of NBS (500 mg, 2.81 mmol) was added, and the reaction mixture was allowed to stir for an additional 24 h. The reaction mixture was added to 50 mL of crushed ice, and a solution of 30% MeOH/70% CHCl3 (100 mL) was stirred in. The layers were separated, and the aqueous portion was extracted with 30% 7-Amino-3-methoxy-1H-1-benzazepine-2,5-dione (15). A mixture of 11 (250 mg, 1.01 mmol), quinoline (20 mg), and Pd/C (10%, 100 mg) in CH2Cl2/MeOH (1:1, 250 mL) was hydrogenated (Parr) at 5 psig for 1 h at 25 °C.…”
Section: -Bromo-3-methoxy-1h-1-benzazepine-25-dione (12)mentioning
confidence: 99%
“…The appearance of the products was monitored by 1 H NMR spectroscopy (Table 2). 18 A 1: 2 ratio of 8, compared to 5 in thermal reactions carried out at 110°C, 19 was observed either in LiOTf or in LiNTf 2 -acetone at room temperature. Another salient feature of the LiOTf-promoted Diels-Alder reaction is the enhancement of the endo/exo selectivity, going from 3.3:1 to 10:1 in the cycloaddition between methyl vinyl ketone and cyclopentadiene ( Table 2, entries 13 and 14).…”
Section: Methodsmentioning
confidence: 97%
“…Much of the recent chemistry has been involved as a key step in the synthesis of complex natural products and will be presented in a later section, The present entries deal with studies that center on the reaction itself. Those products containing quinonoid structures have employed a variety of dienes (142)(143)(144) These problems associated with predicting regioselectivity in quinone DielsAlder chemistry have been studied, and a mechanistic model based on frontier molecular orbital theory has been proposed (150). In certain cases of poor regioselectivity, eg, 2-methoxy-5-methyl-1,4-benzoquinone with alkyl-substituted dienes, the use of Lewis acid catalysts is effective (151).…”
Section: ð36þmentioning
confidence: 99%