Stereodivergent synthesis of highly substituted tetrahydropyrans
Intramolecular oxa-conjugate addition has been employed in a stereoselective synthesis of enantiopure polyalkyl-substituted tetrahydropyrans, which are frequently found as substructures in many natural products. The requisite cyclization precursors, 7-hydroxy-2-enimides 3 and 7- hydroxy-2-enoates 6 were easily accessible by silyloxy Cope rearrangements of the appropriate chiral syn-aldols. It was found that the stereoselectivity of the cyclization could be controlled by judicious choice of the carboxylic acid derivative, resulting in a kinetically controlled reaction for the imides and a thermodynamically controlled process for the esters. Mechanistic considerations that could account for the stereocontrol of the process are outlined.
Schneider, Christoph,Schuffenhauer, Ansgar
p. 73 - 82
(2007/10/03)
Stereodivergent Synthesis of Enantiopure Tetrahydropyrans via the Silyloxy-Cope Rearrangement of Chiral Aldol Products
A stereoselective synthesis of highly substituted and enantiopure tetrahydropyrans from chiral 7-hydroxy-2-alkenoic imides and esters is described. Depending on the carboxylic acid derivative the base-induced cyclization is kinetically or thermodynamically controlled to deliver either tetrahydropyran stereoisomer selectively.
Schneider, Christoph
p. 815 - 817
(2007/10/03)
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