Calculated effect of substitutions on the regioselectivity of cyclization of α-sulfenyl-, α-sulfinyl-, and α-sulfonyl-(5R)-5-hexenyl radicals

Ching Wen Wu, Jia Jen Ho

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17 Citations (Scopus)

Abstract

Calculations of the activation energy of cyclization of α-sulfenyl-, α-sulfinyl-, and α-sulfonyl-5-hexenyl radicals and their respective 5-methyl-5-hexenyl counterparts at the G3MP2B3 level agree quite well with experimental data. The α-sulfinyl-5-hexenyl radical exhibits unexpected regioselectivity (93.99: 6.01) via the 5-exo mode, whereas the α-sulfenyl- and α-sulfonyl-5-hexenyl radicals show increasing branching ratios of the 6-endo product. In contrast, the cyclization of the α-sulfur-based 5-methyl-substituted counterparts yields essentially the 6-endo products in all cases; in particular, the α-SO2-5-CH3-5-hexenyl radical gives high regioselectivity (98.85:1.15) via the 6-endo mode. Several other 5-substituted moieties, including the electron-withdrawing (CN and NO 2) or electron-donating substituents (NH2), also proceed preferentially to 6-endo closure. The α-sulfonyl-5-amine-5-hexenyl radical is calculated to proceed to exclusively the 6-endo product, a demonstration of the high synthetic value of this reactant.

Original languageEnglish
Pages (from-to)9595-9601
Number of pages7
JournalJournal of Organic Chemistry
Volume71
Issue number26
DOIs
Publication statusPublished - 2006 Dec 22

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Regioselectivity
Cyclization
Substitution reactions
Electrons
Sulfur
Amines
Demonstrations
Activation energy

ASJC Scopus subject areas

  • Organic Chemistry

Cite this

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title = "Calculated effect of substitutions on the regioselectivity of cyclization of α-sulfenyl-, α-sulfinyl-, and α-sulfonyl-(5R)-5-hexenyl radicals",
abstract = "Calculations of the activation energy of cyclization of α-sulfenyl-, α-sulfinyl-, and α-sulfonyl-5-hexenyl radicals and their respective 5-methyl-5-hexenyl counterparts at the G3MP2B3 level agree quite well with experimental data. The α-sulfinyl-5-hexenyl radical exhibits unexpected regioselectivity (93.99: 6.01) via the 5-exo mode, whereas the α-sulfenyl- and α-sulfonyl-5-hexenyl radicals show increasing branching ratios of the 6-endo product. In contrast, the cyclization of the α-sulfur-based 5-methyl-substituted counterparts yields essentially the 6-endo products in all cases; in particular, the α-SO2-5-CH3-5-hexenyl radical gives high regioselectivity (98.85:1.15) via the 6-endo mode. Several other 5-substituted moieties, including the electron-withdrawing (CN and NO 2) or electron-donating substituents (NH2), also proceed preferentially to 6-endo closure. The α-sulfonyl-5-amine-5-hexenyl radical is calculated to proceed to exclusively the 6-endo product, a demonstration of the high synthetic value of this reactant.",
author = "Wu, {Ching Wen} and Ho, {Jia Jen}",
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AU - Ho, Jia Jen

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N2 - Calculations of the activation energy of cyclization of α-sulfenyl-, α-sulfinyl-, and α-sulfonyl-5-hexenyl radicals and their respective 5-methyl-5-hexenyl counterparts at the G3MP2B3 level agree quite well with experimental data. The α-sulfinyl-5-hexenyl radical exhibits unexpected regioselectivity (93.99: 6.01) via the 5-exo mode, whereas the α-sulfenyl- and α-sulfonyl-5-hexenyl radicals show increasing branching ratios of the 6-endo product. In contrast, the cyclization of the α-sulfur-based 5-methyl-substituted counterparts yields essentially the 6-endo products in all cases; in particular, the α-SO2-5-CH3-5-hexenyl radical gives high regioselectivity (98.85:1.15) via the 6-endo mode. Several other 5-substituted moieties, including the electron-withdrawing (CN and NO 2) or electron-donating substituents (NH2), also proceed preferentially to 6-endo closure. The α-sulfonyl-5-amine-5-hexenyl radical is calculated to proceed to exclusively the 6-endo product, a demonstration of the high synthetic value of this reactant.

AB - Calculations of the activation energy of cyclization of α-sulfenyl-, α-sulfinyl-, and α-sulfonyl-5-hexenyl radicals and their respective 5-methyl-5-hexenyl counterparts at the G3MP2B3 level agree quite well with experimental data. The α-sulfinyl-5-hexenyl radical exhibits unexpected regioselectivity (93.99: 6.01) via the 5-exo mode, whereas the α-sulfenyl- and α-sulfonyl-5-hexenyl radicals show increasing branching ratios of the 6-endo product. In contrast, the cyclization of the α-sulfur-based 5-methyl-substituted counterparts yields essentially the 6-endo products in all cases; in particular, the α-SO2-5-CH3-5-hexenyl radical gives high regioselectivity (98.85:1.15) via the 6-endo mode. Several other 5-substituted moieties, including the electron-withdrawing (CN and NO 2) or electron-donating substituents (NH2), also proceed preferentially to 6-endo closure. The α-sulfonyl-5-amine-5-hexenyl radical is calculated to proceed to exclusively the 6-endo product, a demonstration of the high synthetic value of this reactant.

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