Unusual strain-releasing nucleophilic rearrangement of a bicyclo[2.2.1]heptane system to a cyclohexenyl derivative
2012 (English)In: Journal of Organic Chemistry, ISSN 0022-3263, E-ISSN 1520-6904, Vol. 77, no 21, 9747-9755 p.Article in journal (Refereed) Published
We report an unusual strain-releasing reaction of 1-mesyloxy-8,7- dimethylbicyclo[2.2.1]heptane (3) by a base-promoted substitution at the chiral C3 followed by spontaneous concerted ring opening involving the most strained C2-C3-C4 bonds (with bond angle 94°) and the C2 bridgehead leading to anti-endo elimination of the C1-mesyloxy group by the conjugate base of adenine or thymine to give two diastereomeric C3′(S) and C3′(R) derivatives of 1-thyminyl and 9-adeninyl cyclohexene: 3 → T-4a + T-4b and 3 → A-5a + A-5b. These products have been unambiguously characterized by detailed 1D and 2D NMR (J-coupling constants and nOe analysis), mass, and UV spectroscopy. Evidence has been presented suggesting that the origin of these diastereomeric C3′(S) and C3′(R) derivatives of 1-thyminyl and 9-adeninyl cyclohexene from 3 is most probably a rearrangement mechanism of a trigonal bipyramidal intermediate formed in the S N2 displacement-ring-opening reaction.
Place, publisher, year, edition, pages
2012. Vol. 77, no 21, 9747-9755 p.
IdentifiersURN: urn:nbn:se:uu:diva-184927DOI: 10.1021/jo301871dISI: 000311190200034OAI: oai:DiVA.org:uu-184927DiVA: diva2:570494