4-tert-Butyl cyclohexyl bromide

Further insight into the E2 mechanism comes from stereochemical studies One such experiment compares the rates of elimination of the cis and trans isomers of 4 tert butyl cyclohexyl bromide... 

Aliphatic Ketones The asymmetric hydrogenation of simple aliphatic ketones remains a challenging problem. This may be attributed to the difficulty with which the chiral catalyst differentiates between the two-alkyl substituents of the ketone. Promising results have been obtained in asymmetric hydrogenation of aliphatic ketones using the PennPhos-Rh complex in combinahon with 2,6-lutidine and potassium bromide (Tab. 1.11) [36]. For example, the asymmetric hydrogenation of tert-butyl methyl ketone affords the requisite secondary alcohol in 94% ee. Similarly, isopropyl, Butyl, and cyclohexyl methyl ketones have been reduced to the corresponding secondary alcohols with 85% ee, 75% ee, and 92% ee respectively. 

None of these compounds has structural features necessary to promote SnI (not even the third notice that the bromine is attached to a primary carbon, even though there is a tert-butyl group in the molecule), so we need to think about Sn2 reactivity only. In general, steric hindrance slows dovm Sn2 reactions, so we can start by saying that methyl bromide > -butyl bromide > cyclohexyl bromide. But how do the other two fit into the scale An adjacent carbonyl group accelerates Sn2 reactions enormously, so the ketone will react even faster than methyl bromide. On the other hand, a bulky tert-butyl group adjacent to a reaction centre leads to very slow substitution, so this compound ( neopentyl bromide ) goes at the bottom of the scale. 

Li and coworkers reported the conjugate addition of alkyl groups to enamides mediated by zinc in aq. NH4CI to generate a -amino acid derivatives (Eq. 4.73). No reaction was observed in the absence of water. Both secondary and tertiary alkyl groups such as linear (2-butyl, 2-propyl, 2-pentyl), cyclic (cyclohexyl, cyclopentyl, cycloheptyl), and bulky ones (tert-butyl) were all transferred to the substrate successfully. Even simple primary iodides and methyl iodide provided the desired products in good yields. Miyabe et al. as well as Jang and Cho reported the addition of alkyl radicals from alkyl iodide to a,p unsaturated ketones, esters, and nitriles mediated by indium in aqueous media. Indium-mediated Michael addition of allyl bromide to l,l-dicyano-2-arylethenes also proceeded well in aqueous medium. ... 

RX. n-butyl bromide n-dodecanyl iodide cyclohexyl iodide ethyl bromo acetate methyl 2,3-di-O-acetyl-4-O-benzoyl-6-bromo-6-deoxy-ot-D-glucopyranoside methyl 2,3,4-tri-0-acetyl-6-deoxy-6-iodo-0 -D glucopyranoside l,2 3,4-di-0-isopropylidene-6-deoxy-6-iodo-a-D-galactopyranose methyl 2(R)-[(tert-butoxycarbonyl)amino]-3-iodo-propionate cyclic bis(trifluoromethyl)oxazolidinone bromide. 

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