Alkyl scrambling

There are few studies that address relative isomer stability of substituted magnesocenes. For example, the acid-catalyzed transalkylation (alkyl scrambling) studies of disubstituted benzenes would destroy the organometallic of interest. One suggestive... 

Multiple Alkyl Scrambling with Ring Expansion... 

Alkyl scrambling due to fhe transfer of fhe wrong alkyl group from fhe stannyl derivative onto fhe aryl species... 

Alkyl scrambling has been reported to occur more frequently with trimefhyl-stannyl than with tributylstannyl derivatives [188]. 

Scheme 2.58 P-aryl/P-alkyl scrambling and formation of benzaldehyde during rhodium-catalyzed hydroformylation.

On the other hand, aryl-alkyl scrambling can cause a serious work-up problem when TPPMS is used in an aqueous two-phase reaction (Scheme 2.59)... 

Scrambling reactions occur between R4Sn and SnX4 to give mixed alkyl halides. 

The complex TpPtMeH2 was synthesized by reacting TpPtMe(CO) with water (66). While it is stable towards reductive elimination of methane at 55 °C, deuterium incorporation from methanol-c/4 solvent occurs rapidly into the hydride positions and subsequently, more slowly, into the methyl position (Scheme 15). The scrambling into the methyl position has been attributed to reversible formation of a methane complex which does not lose methane under the reaction conditions (75,76). Similar scrambling reactions have been observed for other metal alkyl hydrides at temperatures below those where alkane reductive elimination becomes dominant (77-84). This includes examples of scrambling without methane loss at elevated temperature (78). 

The thermodynamic stabilities of phenonium ions relative to the parent have been determined in the gas phase by measuring the position of the equilibrium between (46) and (47)7 The results followed a Yukawa-Tsuno relationship with a p value of -12.6 and an r+ value of 0.62, the general behaviour being more like benzenium ions than benzyl cations, with tt-delocalization less effective than in benzyl cations. A theoretical study of the elimination of molecular H2 from the benzenium ion C6H7+ shows that the barrier to this process appears to be very small.The gas-phase Friedel-Crafts alkylation reaction of CF3C6L6+ (L = H or D) with C2L4 is accompanied by isotopic scrambling, which has been used to elucidate the mechanism of this process. A theoretical calculation shows that the lifetime of triplet phenyl cation must be very short. ... 

Perhaloalkanes have been found to scramble halogen atoms via consecutive halophilic reactions following carbanion generation by halophilic attack by base. S l reaction of an allylsilane has been applied in a stereocontrolled synthesis of ( )-dihydronepetalactone, and functionalized aryl and arylmethyl carbanions have been generated by reductive cleavage of aryl and arylmethyl alkyl ethers by electron transfer from alkali metals. ... 

The alkyl groups scramble during the reaction (36). When a mixture of two different dialkylzinc agents, R 2Zn and R22Zn, is used, a statistical distribution of the possible alkylation products is obtained (Scheme... 

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