Ws. Chung et al., FACE SELECTIVITY IN THE PATERNO-BUCHI REACTIONS OF METHACRYLONITRILE TO 5-SUBSTITUTED ADAMANTAN-2-ONES, Perkin transactions. 2, (3), 1995, pp. 581-586
The photocycloaddition of methacrylonitrile to 5-substituted adamantan
-2-ones (1-X) produces two geometrically isomeric oxetanes in which th
e oxygen atom and the 5-substituent are in anti or syn positions. The
substituent was varied from fluoro, chloro, bromo, phenyl to SiMe(3) a
nd the product ratios, except for SiMe(3), were similar (ca. 56:44) in
all instances. Structure determination of the anti and syn oxetanes w
ere carried out by H-1 and C-13 NMR and mass spectroscopy. The structu
re of syn-5-bromospiro[adamantane-2,2'-oxetane] (syn-5-Br) was further
supported by single-crystal X-ray crystallography. The product format
ion bias resulting from the attack on the zu-face is discussed in term
s of transition-state hyperconjugation, but new results for photocyclo
addition reactions of 5-trimethylsilyl-substituted adamantan-2-one (1-
SiMe(3)), with both fumaronitrile and methacrylonitrile, show an unpre
cedented sigma-electron-withdrawing characteristic with this substitue
nt.