H0fmann elimination (conversion into the hydroxide with silver oxide/water ; 12 hours' heating in boilingxylene with a water separator, addition of phenothiazine) into a mixture of diastereomeric quadruple-layered tetramethoxy[2.2]paracyclophanes (3) and ( 4 ) (ratio of 1 : 2). The diastereomers could be separated by repeated fractional crystallization from toluene/acetone (2 : 3): (3~[31 forms colorless platelets (from acetone), dec. >265'C; MS, M + calc. for c 4 ~H 4 4 0 4 588.3239, exp. 588.3243; mass spectrometric fragmentation corresponds to the [2.2]paracyclophane structure: m/e=588 (M+, 80%), 424 (40%), 294 (100%); 'H-NMR (80 4H), 5.53 (s, 4H). (4)[31 is obtained from its acetone solution as colorless needles of m.p. 263-265'C (dec.); MS, M' exp. 588.3243, ~/ e = 5 8 8 (M', loo%), 424 (46%), 294 (97%); 5.46 (s, 4H), 5.68 (s, 4H). Assignment of ( 3) and ( 4), and hence also that of the derived compounds (j)/(l) and ( 6) / ( 2) , is based on the crystal structure of (3), which requires a molecular center of symmetry for this d i a ~t e r e o m e ~~] . MHz, c 6 D ~) : ~=2.1-3.6 (m, 24H), 3.31 ( S , 12H), 5.45 ( S , 'H-NMR(8OMHz,C6H6):~=2.1-3.6(m,24H),3.28 (s, 12H), Me0 OMe Me0
Demethylation of ( 3 ) and ( 4 ) was accomplished with methylmagnesium
(5 equiv., 3 h, 130-l4O0C, under nitrogen). After oxidation with siIver(1) oxide (acetone, 1 h), chromatography (silica gel plates, chloroform) gave three fractions: R ~~0 . 5 7 , 5 0 ~7 0