A Novel 1,2-Migration of Acyloxy, Phosphatyloxy, and Sulfonyloxy Groups in Allenes: Efficient Synthesis of Tri- and Tetrasubstituted Furans

摘要

[3,3] Migrations of propargylacyloxy, phosphatyloxy, and sulfonyloxy groups are important transformations in organic synthesis. In addition to these sigmatropic migrations, radical 1,2-acyloxy and -phosphatyloxy migrations [Eq. (1)] have been used extensively in carbohydrate and nucleoside chemistry. 1,2-Acyloxy migration has also been proposed as a key step in the Pd-catalyzed propargyl-propenyl isomerization [Eq. (2)]. In both cases, 1,2-migration of acetate or phosphate proceeds from an sp~3 carbon. To the best of our knowledge, no 1,2-migrations of the acyloxy, phosphatyloxy, and sulfonyloxy groups from an sp~2 carbon have been disclosed. Herein we wish to report a novel 1,2-migration of the acyloxy, phosphatyloxy, and sulfonyloxy groups in the allenyl system [Eq. (3)]. This unprecedented migration, incorporated into the cycloisomerization reaction, is the key to an efficient synthesis of valuable tri- and tetrasubstituted furans.