THERMAL AND ELECTRON-TRANSFER-INDUCED REACTIONS OF ENEDIYNES AND ENYNE-ALLENES .5. FIRST ISOLATION OF 2 ROTAMERS ABOUT THE P-C BOND IN A PHOSPHANE OXIDE

The thermal cyclization of the phosphane oxide substituted enyne-allen e 1d results in the formation of 4d, an unknown double-bond shift isom er of the 11H-benzo[b]fluorene system, Because of the completely hinde red rotation about the P-C bond, two rotamers could be isolated and id entified on the basis of their spectral data. No thermal interconversi on between the two rotamers was observed.