Überbrückte [14]Annulene mit Phenanthren-Perimeter:syn-1,6:7,12-Bismethano[14]annulen

Abstract

der Organolutetium-Phosphor-Bi!dungen (erstmals gemessen) betragen 2.782 und 2.813 A.[**I Diese Arbeit wurde von der Deutschen ForschungsgemeinschafI gef6r-Angew. Chem. 98 (1986) Nr. 8 0 VCH Verlagsgeselhchaft mbH. D-6940 Weinheim. 1986 0044-8249/86/08M-0729 S 02.50/0

Low Valent Titanium - A versatile reagent for deoxygenation and carbonyl coupling. 11

“…The essential value of the carbonyl coupling reaction for organic synthesis lies in the fact that intramolecular couplings of dicarbonyl compounds take place in good yields to give cycloalkenes [15]. From the numerous reported synthetic applications of this methodology only two are mentioned as examples: In the synthesis of fusicocca-2,8,10(14)-triene (7) the central eight-membered ring was closed by the reductive coupling of two aldehyde groups [16] and the cyclic 14electron .ir-system 9 was obtained from the dicarbonyl precursor 8 in 40 YO yield [17]. It should be noted that titanium-induced dicarbonyl couplings, like other cyclisation reactions to form medium and large rings, require high dilution conditions in order to realise intramolecular cyclisation rather than intermolecular polymerisation.…”