8-phosphabicyclo[3.2.1]octanes—II: The synthesis and stereochemistry of 8-phosphabicyclo[3.2.1]oct-6-enes

Several new 8-phosphabicyclo3.2.1]oct-6-enes and -6-en-3-yl acetates were prepared by the alkyl (or aryl)dihalophosphane addition to cyclohepta -1,3-diene and 1-acetoxy cyclohepta-3,5-diene. The P-configuration in two P-epimer pairs (3, 4 and 5, 6) and three other compounds which were each obtained as a single isomer (1, 2 and 7) was determined by investigation of the NMR spectra, i.e. by complexation of the compounds with Eu(dpm)₃ as well as from the various phosphorus-hydrogen coupling constants. Compounds possessing the same P-substituent were correlated among themselves and in the case of the PPh bearing compounds (1 and 7) further correlation to a known compound (8a) was established. The chemical behaviour of the C₆C₇ double bond is discussed and compared with the corresponding behaviour in trop-6-enes. Great steric hindrance was found for this bond, for which the following sequence is suggested:

The synthesis of a phosphaatropine analog is described.