ChemInform Abstract: CYCLIC UNSATURATED COMPOUNDS. LIX. ACETOXYCYCLOPENTADIENE

Abstract

Aus dem Acetoxydicyclopentadien (I) entsteht bei 185‐195°C unter Cyclopentadien‐Eliminierung ein Gemisch isomerer Diacetoxydicyclopentadiene (II); die Depolymerisation dieses Dimerengemisches bei 400°C (im Quarz‐Rohrreaktor) liefert ein 1:3‐Gemisch der Acetoxycyclopentadien‐Isomeren (III) und (IV).

π-Facial stereoselectivity in the Diels–Alder reactions of benzene oxides

“…The adduct was symmetrical, i.e., it was derived from 7 and not from 8. 4 Irradiation of the methyl singlet in the 'H nmr resulted in a significant nOe of the signal due to the protons a to the carbonyls, and vice versa. Thus, the structure of the adduct could only have been 9, the product of endo addition, anti to the oxygen.…”

“…Double dehydrobromination was effected with DBU. The 'H nmr of the product displayed a single set of signals, but Vogel and Giinther (13) demonstrated that this is really an average of the signals of benzene oxide (3) and its valence tautomer, oxepin (4). The addition of N-phenylmaleimide to an ether solution of the tautomeric mixture resulted in smooth conversion to a single adduct.…”

“…Other heteroatoms in a similar position force the cycloaddition to take place mainly anti to the heteroatom (2,3), as do simple hydrocarbon substituents (4). * Other cyclic and acyclic systems with allylic heteroatom substituents have been examined: some add syn while others add anti (6).…”