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ChemInform Abstract: Efficient Syntheses of Thiochromans via Cationic Cycloadditions.
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2001 cycloaddition reactions cycloaddition reactions O 0070 48 - 043 Efficient Syntheses of Thiochromans via Cationic Cycloadditions. — Starting from α-benzotriazolyl sulfides (I) or (IX), three types of thiochromans are synthesized: 2,4-diaryl-, 2,4-diaryl-4-methyl-, and 2,3,4-trisubstituted chromans. By treatment of the starting sulfides with ZnBr 2 in the presence of various alkenes, the generated thionium ions undergo cycloaddition with the alkenes to give mixtures of diastereomers which are separated in most cases to give pure major diastereomers. The reactions can be either performed at room temperature for 14-18 h or at reflux for ca. 4 h. The reaction temperature has negligible effect on yield or diastereoselectivity. — (KATRITZKY, ALAN R.; BUTTON, MARTIN A. C.; J. Org. Chem. 66 (2001) 16, 5595-5600; Cent. Heterocycl. Compd., Univ. Fla., Gainesville, FL 32611, USA; EN) 1
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Transcript of ChemInform Abstract: Efficient Syntheses of Thiochromans via Cationic Cycloadditions.
2001 cycloaddition reactions
cycloaddition reactionsO 0070
48 - 043Efficient Syntheses of Thiochromans via Cationic Cycloadditions. —Starting from α-benzotriazolyl sulfides (I) or (IX), three types of thiochromansare synthesized: 2,4-diaryl-, 2,4-diaryl-4-methyl-, and 2,3,4-trisubstitutedchromans. By treatment of the starting sulfides with ZnBr2 in the presence ofvarious alkenes, the generated thionium ions undergo cycloaddition with thealkenes to give mixtures of diastereomers which are separated in most cases togive pure major diastereomers. The reactions can be either performed at roomtemperature for 14-18 h or at reflux for ca. 4 h. The reaction temperature hasnegligible effect on yield or diastereoselectivity. — (KATRITZKY, ALAN R.;BUTTON, MARTIN A. C.; J. Org. Chem. 66 (2001) 16, 5595-5600; Cent.Heterocycl. Compd., Univ. Fla., Gainesville, FL 32611, USA; EN)
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