1-Bromo-l-methyl-2,2-diphenylcyclopropan

An entirely different result has been reported by Jacobus and Pensak. They found that the reduction of the optically active 1-bromo-l-methyl-2,2-diphenylcyclopropane (51) with sodium naphthalenide (NaN) in DME (0.5 m) yields the corresponding hydrocarbon 49 of 29% optical purity with net retention of configuration. This observation was interpreted to mean that the l-methyl-2,2-diphenylcyclopropyl (t radical was being captured by a second SET from sodium naphthalenide to give the sodium derivative (which transforms in DME to 49) at a rate faster than its inversion frequency (Scheme 14). 

Oxidative decarboxylation of optically active l-methyl-2,2-diphenylcyclopropanecarboxylic acid (10) with lead tetraacetate in the presence of iodine leads to racemized 1-iodo-l-methy 1-2,2-diphenylcyclopropane (11) in 45% yield. Subjecting 10 to the Cristol-Firth modification of the Hunsdiecker reaction (bromine and mercuric oxide in carbon tetrachloride) leads to racemic 1-bromo-l-methyl-2,2-diphenylcyclopropane (12) however, the yield is poor (5 /o). ... 

Rieke magnesium. Mg, allows the formation of Grignard reagents at low temperatures. (S)-( + ) 1-bromo-l-methyl-2,2-diphenylcyclopropane e.g., on reaction with Mg at - 65 °C, yields a chiral Grignard reagent that is 33-43% optically pure [40]. 

On the other hand, in studies [50] on the optical purity of organolithium compounds derived from ( + )-(S) 1-bromo-l-methyl-2,2-diphenylcyclopropane (see Sect. 4.3.2, pp. 144-146) it was demonstrated that the nature of the lithium surface, as well as the purity of the metal did influence the results. 

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See also in sourсe #XX -- [ , , ]

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