Carbonyl Transposition and Regio- and Stereo-specific Syntheses of New Alcohols, Amino-alcohols, and Ketones in the Monoterpenoid 1,3,3-Trimethyl-2-oxabicyclooctane

Article abstract of DOI:10.1039/P19800002626

An efficient transposition of carbonyl group R¹-CO-CH2-R² -> R¹-CH2-CO-R² in the 1,3,3-trimethyl-2-oxabicyclo<2.2.2>octane system was carried out via hydroboration-oxidation of 6-dialkylamino-1,3,3-trimethyl-2-oxabicyclo<2.2.2>oct-5-enes (3a-c), which gave regio- and stereo-specifically 6-cis-dialkylamino-1,3,3-trimethyl-2-oxabicyclo<2.2.2>octan-5-trans-ols (4a-c) in high yield.Cope reaction on the N-oxide (5b) obtained from the amino-alcohol (4b) with hydrogen peroxide led to 1,3,3-trimethyl-2-oxabicyclo<2.2.2>octan-5-one (6), the other possible isomer of the long-known 1,3,3-trimethyl-2-oxabicyclo<2.2.2>octan-6-one (1b).The ketone (6) was also obtained from 1,3,3-trimethyl-2-oxabicyclo<2.2.2>oct-5-ene (2) via its trans-epoxide (11), lithium aluminium hydride reduction at 160-165 deg C of which gave stereo- and regio-specifically 1,3,3-trimethyl-2-oxabicyclo<2.2.2>octan-5-trans-ol (9b).Chromic acid oxidation of (9b) and (4a-c) under various conditions gave the ketone (6) and the amino-ketones (7a-c), respectively.Lithium aluminium hydride reduction of (6) and (7a-c) afforded stereospecifically the cis-alcohol (9a) and 6-cis-dialkylamino-1,3,3-trimethyl-2-oxabicyclo<2.2.2>octan-5-cis-ols (8a-c), respetively.Hydroboration-oxidation of the alkene (2) was not regiospecific, giving a 3:1 mixture of the trans-alcohols (9b) and (10b), respectively.

Full text of DOI:10.1039/P19800002626

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