Stereochemical study on an oxygen-directed olefin oxidation and subsequent oxygen cyclization: Differences between peracid and metal oxide-catalyzed hydroperoxide in oxidation reactions

Optically active (2S,4R)-2-hydroxy-4-pentyl enol ether was prepared for the first time and subjected to hydroxy-directed oxidations at the olefinic group. Treatment with m-chloroperbenzoic acid and tert-butyl hydroperoxide/vanadium acetylacetonate resulted in the same stereoface differentiation at the olefin, with diastereomeric excesses as high as 79% and 92%, respectively, whereas the stereochemistry of the products of subsequent nucleophilic additions of the hydroxy group was opposite.

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(2S,4R)-4-(Cyclohex-1-en-1-yloxy)pentan-2-olC11H20O2[α]D23=+51.0 (c 0.52, CH2Cl2)Absolute configuration: (2S,4R)Source of chirality: (2R,4R)-2,4-pentanediol

C19H26O4(2S,4R)-4-(Cyclohex-1-en-1-yloxy)pentan-2-yl 4-methoxybenzoate[α]D23=+23.0 (c 1.02, CH2Cl2)Absolute configuration: (2S,4R)Source of chirality: (2R,4R)-2,4-pentanediol