Synthesis of Fluorocyclobutanones and Their Use in the Synthesis of Fluoronucleosides.

Abstract

Nucleic acids U 0700Synthesis of Fluorocyclobutanones and Their Use in the Synthesis of Fluoronucleosides. -Fluorocyclobutanones (IV) and (VI) are prepared by replacement of a hydroxyl group with fluoride by DAST. The photolytic reaction of cyclobutanones (VI) and (X) with chloropurine leads to the corresponding fluorinated nucleosides. -(GHAZI, H.; LEE-RUFF*, E.; J. Fluorine Chem. 126 (2005) 11-12, 1565-1569; Dep. Chem., York Univ., North York, Toronto, Ont. M3J 1P3, Can.; Eng.) -R. Staver

Photochemical Generation of 9H‐Fluorenyl Radicals

“…The van der Waals volume of CF 3 is slightly larger than for CH 3 (atomic radii of 1.35 Å for F vs 1.17 Å for H) . Coupled with the larger dipolar nature of the C–F bond results in significant repulsion in 1 R=CF 3 as compared to 1 R=CH 3 in their gauche conformations as shown by their crystal structures and computation.…”

“…The parent bifluorenyl 1 R=H shows a DΗ † which is 11.7 kcal mol À1 larger than for the dimethyl analog 1 R=CH 3 (10). Fluorine can also be regarded as an isopolar mimic of the OH group (31). As such hydrogen bonding effects can play a major role for these reactions.…”