ISSN:
0009-2940
Keywords:
Atropisomerism
;
Biphenyl derivatives
;
Phosphonium ylides
;
Rearrangements
;
Helical structures
;
Chemistry
;
Inorganic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Phosphine Alkylidenes, 491). - Chemistry and Stereochemistry of 9,10,19,20-Tetrahydrotetrabenzo[a,c,g,i]cyclododecene and of Some DerivativesTwofold intermolecular C alkylation of the bis-ylide 4 with the dibromide 5 and subsequent hydrolysis yields meso-9,10,19,20-tetrahydrotetrabenzo[a,c,g,i]cyclododecene (1 b), which isomerizes on heating to give the racemate 1a. From 1a and 1b the isomeric dibromides 7-10 are synthesized. Reaction of 7-10 with phenyllithium leads to the formation of the polycyclic compounds 11, 12, 13, from which 12 may be dehydrogenated to the unsaturated compound 14. Reaction of the dibromides 7-10 with silver acetate occurs with retention yielding the acetates 15-18, which may be hydrolysed to the corresponding alcohols. With the knowledge of the structures of compounds 15-22 the stereochemistry of the synthesis and the Wittig ether rearrangement of the diethers 24 can be elucidated. In the reaction of the dibromides 7-10 with sodium acetate elimination takes place instead of substitution. Starting from 7 and 8 the polycyclic hydrocarbon 31 is formed via the carbenium ion intermediate 26 and subsequent transannular reaction. 31 is dehydrogenated to yield 32, whose X-ray structural analysis shows a multi helical structure. Reaction of the base potassium tert-butylate with the dibromides 7-10 leads to the formation of isomers of the diolefin 2.
Additional Material:
4 Tab.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/cber.19911241219
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