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Synthesis of alpha-ketoester- and alpha-hydroxyester-substituted isoindazoles via the thermodynamic coarctate cyclization of ester-terminated azo-ene-yne systems.

ABSTRACT: The synthesis of isoindazoles bearing alpha-ketoester and alpha-hydroxyester groups via the coarctate cyclization of ester-terminated azo-ene-yne precursors is described. Whereas previous studies on isoindazole formation have shown the reaction to proceed through a kinetic coarctate pathway, functionalization of the terminal acetylene with a methyl ester sufficiently stabilizes the carbene intermediate to make the coarctate cyclization the thermodynamic pathway. Density functional theory (DFT) computations reveal ca. 8-9 kcal mol(-1) lower energy transition states for the coarctate pathway compared to the parent system.

SUBMITTER: McClintock SP

PROVIDER: S-EPMC4154358 | biostudies-literature | 2009 Sep

REPOSITORIES: biostudies-literature

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Synthesis of alpha-ketoester- and alpha-hydroxyester-substituted isoindazoles via the thermodynamic coarctate cyclization of ester-terminated azo-ene-yne systems.

McClintock Sean P SP Forster Nathan N Herges Rainer R Haley Michael M MM

The Journal of organic chemistry 20090901 17

The synthesis of isoindazoles bearing alpha-ketoester and alpha-hydroxyester groups via the coarctate cyclization of ester-terminated azo-ene-yne precursors is described. Whereas previous studies on isoindazole formation have shown the reaction to proceed through a kinetic coarctate pathway, functionalization of the terminal acetylene with a methyl ester sufficiently stabilizes the carbene intermediate to make the coarctate cyclization the thermodynamic pathway. Density functional theory (DFT) c ...[more]

PMID: 19642649

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