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Non-bonding 1,5-S···O interactions govern chemo- and enantioselectivity in isothiourea-catalyzed annulations of benzazoles.

ABSTRACT: Isothiourea-catalyzed annulations between 2-acyl benzazoles and ?,?-unsaturated acyl ammonium intermediates are selectively tuned to form either lactam or lactone heterocycles in good yields (up to 95%) and high ee (up to 99%) using benzothiazole or benzoxazole derivatives, respectively. Computation gives insight into the significant role of two 1,5-S···O interactions in controlling the structural preorganization and chemoselectivity observed within the lactam synthesis with benzothiazoles as nucleophiles. When using benzazoles the absence of a second stabilizing non-bonding 1,5-S···O interaction leads to a dominant C-H···O interaction in determining structural preorganization and lactone formation.

SUBMITTER: Robinson ERT

PROVIDER: S-EPMC5450589 | biostudies-literature | 2016 Dec

REPOSITORIES: biostudies-literature

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Non-bonding 1,5-S···O interactions govern chemo- and enantioselectivity in isothiourea-catalyzed annulations of benzazoles.

Robinson Emily R T ERT Walden Daniel M DM Fallan Charlene C Greenhalgh Mark D MD Cheong Paul Ha-Yeon PH Smith Andrew D AD

Chemical science 20160704 12

Isothiourea-catalyzed annulations between 2-acyl benzazoles and α,β-unsaturated acyl ammonium intermediates are selectively tuned to form either lactam or lactone heterocycles in good yields (up to 95%) and high ee (up to 99%) using benzothiazole or benzoxazole derivatives, respectively. Computation gives insight into the significant role of two 1,5-S···O interactions in controlling the structural preorganization and chemoselectivity observed within the lactam synthesis with benzothiazoles as nu ...[more]

PMID: 28567263

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