2.2- Diphenyl-1 - cyclopropane

Cyclopropane, 1,1-diphenyl-, 48, 75 Cyclopropanols, synthesis of 1-substi-tuted, 47,110 Cyclotetradecanone, 48, 58... 

Diphenyl-propen-(2)-saure wird durch Lithiumalanat in 57—62%iger Ausbeute zu 1,1- Diphenyl- cyclopropan cyclisiert1 ... 

Diphenyl-1,3-propandiol wird dagegen mit Titan(III)-chlorid/Lithiumalanat zu ei-nem Gemisch aus 12°/0 cis- und 49% trans- ,2-DiphenyI-cyclopropanJ 20% 1,3-Diphe-nyl-propanol, 15% 1,3-Diphenyl-propan und 5% trans-1,3-Diphenyl-propen (Gesamt-ausbeute der Cyclopropan-Verbindungen 40% d.Th.) reduziert3 ... 

Die Reduktion geminaler Dibrom-cyclopropane mit Chrom(II)-acetat in Dimethylsulf-oxid fiihrt (in Abhangigkeit von Zeit und Temperatur) zu wechselnden Mengen an Brom-cyclopropanen. Aus 2,2-Dibrom-1,1-diphenyl-cyclopropan entsteht dagegen ausschlieB-lich 1,1 -Diphenyl-allen (s. S.517), in waBr. Dimethylformamid entstehen zusatzlich Aeetoxy-Derivate4 ... 

Cyclopropane konnen sich je nach Substitution bei der Reduktion mit Chrom(II)-Sal-zen zu verschiedenen Produkten umlagern (vgl. a. S. 5101). l,l-Dibrom-2,2-diphenyl-cyclopropan reagiert mit Chrom(Il)-acetat in Dimethylsulfoxid3 oder Chrom(III)-chlo-rid/Lithiumalanat4 zum 1,1-Diphenyl-alien ... 

Beim BenzoyI-cyclopropan(- 1,38 V) erhalt man dagegen neben 1-Oxo-l-phenyl-butan iiberwiegend infolge Dimerisierung 1,2-Dicyclopropyl- , 2-diphenyl-glykolb. 

The photochemistry of l,l,5,5-tetraphenyl-3,3-dimethyl-l,4 pentadiene (1) has been studied in detail by Zimmerman and Mariano.<7) Photolysis of compound (1) gave 1,1-diphenyl-2,2-dimethyl-3-(2,2-diphenylvinyl) cyclopropane ... 

The specific feature of the bonds also affects its chemical behaviour and the stereochemistry of substitution reactions. For example in the conversion of (-) trans -2, 3 diphenyl cyclopropane carboxylic acid into (+) 1, 3 diphenylallene the optical activity is retained. 

Mann and Barnes [45] have discussed the mechanism of reduction of substituted and optically active 1-bromo-and 1-iodocyclopropanes, and Hazard and coworkers [46] have investigated the reduction of l-bromo-l-carboxy-2,2-diphenyl-cyclopropane. At mercury cathodes, electrolyses of 1-bromo- and 1-iodonorbornane proceed via two-electron cleavage of the carbon-halogen bond to give mainly nor-bomane, plus a small amount of bis(l-norbomyl)mercury [47]. 

Cleavage Gem-dihalides and monohalides have been dehalogenated to chiral monohalides in the presence of alkaloids [397, 398]. l,l-Diphenyl-2-bromo-2-carboxyl (bromo or methyl carboxylate) cyclopropanes are cathodically debromi-nated in the presence of alkaloid cations with enantioselectivities up to 45% ee. A mechanism is proposed whereby the alkaloid is adsorbed at the Hg cathode, which protonates face selectively the carbanion generated by 2e reduction from the bromide [399]. 

The photolysis of diphenyl-diazomethane in cis-jS-deutero-styrene, on the other hand, can be affected by dilution with hexafluorobenzene. The amount of trans-cyclopropane 49 is slightly larger, indicating that about 12% of the singlet carbene are still present in very dilute solutions (see Table 9). 

A second example of the use of ionic chiral auxiliaries for asymmetric synthesis is found in the work of Chong et al. on the cis.trans photoisomerization of certain cyclopropane derivatives [33]. Based on the report by Zimmerman and Flechtner [34] that achiral tmns,trans-2,3-diphenyl-l-benzoylcyclopropane (35a, Scheme 7) undergoes very efficient (0=0.94) photoisomerization in solution to afford the racemic cis,trans isomer 36a, the correspondingp-carboxylic acid 35b was synthesized and treated with a variety of optically pure amines to give salts of general structure 35c (CA=chiral auxiliary). Irradiation of crystals of these salts followed by diazomethane workup yielded methyl ester 36d, which was analyzed by chiral HPLC for enantiomeric excess. The results are summarized in Table 3. 

Scheme 7 Photoisomerization of salts of frans,frans-2,3-diphenyl-1-benzoyl-cyclopropane-p-carboxylic acid...

The diozonolysis of cyclo-1,3-dienes leads to a mixture of substituted 1,2-dioxanes <1990OJO1369, 19890B145> the product composition, but not the stereochemistries of the reaction products, was determined by H and O NMR spectroscopy. 3,3-Diphenyl-l,2-dioxan-4-one was isolated and characterized by H NMR spectroscopy as one reaction product of the ozonolysis of (diphenylmethylene)cyclopropane <2001HCA1943>. 

Recently, the cyclopropanation of (Z)-4-benzyIidene-2-phenyl-5(4//)-oxazolone 621 with phenyldiazomethane was reported to give the spirocyclopropane, rac- 21 in very high yield. Subsequent ring opening and hydrolysis of rac- 21 generated frani-l-amino-2,3-diphenyl-l-cyclopropanecarboxylic acid, rac-828 (cadiPhe) (Scheme 7.256). This new, constrained phenylalanine analogue induces a y-tum in the sohd state when incorporated into model dipeptides. The enantiomers of the Al-Boc (Boc = tert-butyloxycarbonyl) methyl ester of 828 have been resolved by HPLC. 

PENTAMETHYL-, 56, 1 Cyctopentane, acetyl-, 55, 25 Cyclopentane, 1-cyano-l-phenyl-, 55, 94 Cyclopentane, methyl, 55, 62 Cyclopentanol p-toluenesulfonate, 55, 112 Cyclopentene, 56, 34, 58, 73 2-Cyclopenten-l-one, 2,5-dialkyl- 58, 62 CYCLOPENTENONES, 58, 56 Cyclopropane, 1 -acetyl-1 -phenyl-, 55, 94 Cyclopropane, 1, l-dibromo-2,2-diphenyl-, 56, 32... 

Photostationary cis/trans ratios vary with sensitizer structure in a manner not yet perfectly understood, and both the time required for attainment of a photostationary state and actual flash spectroscopic quenching rates indicate that energy transfer to diphenylcyclopropane is quite inefficient. Such should be the case if nonvertical energy transfer with the production of a biradical is occurring. When care is taken so that only the sensitizer absorbs light, only cis-trans isomerization is observed. Direct excitation of the cyclopropane produces 1,3-diphenyl-propene and 1-phenylindane as well.298... 

Gamma irradiation of benzene solutions of 1,2-diphenylcyclo-propane also results in cis-trans isomerization, presumably by energy transfer from triplet benzene.300 G values for isomerization are close to one. Gamma irradiation of the neat cyclopropane produces high G values for geometric isomerization and only traces of 1,3-diphenyl-propene. 

---