Direct Synthesis of 1,3-Dien-2-yl Esters from α-Allenols and Carboranyl Carboxylic Acids

초록

We report a metal- and base-free intermolecular O-1,3-dien-2-ylation of C-carboxylated carboranes with alpha-allenols, enabling direct access to carborane-containing 1,3-dien-2-yl esters under mild conditions. This operationally simple protocol proceeds via dehydration of a protonated alpha-allenol to generate a putative alpha-allenyl carbocation, which is efficiently intercepted by the corresponding carboranyl carboxylate. The synthetic utility of the resulting dienyl esters is demonstrated through Diels-Alder reactions with representative dienophiles. Mechanistic investigations support the unique reactivity of carboranyl carboxylic acids and a pathway distinct from transition-metal-catalyzed intramolecular acyloxy migration manifolds.

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