Neomenthyl esters

On the other hand, in the oxidation of frans-cyclohexane-based substrates, oxidation at methylenic positions was found to be in competition with that of tertiary C-H bonds. fra s-l,2-DMCH yielded a normalized 24 76 3°/2° ratio, and this trend was even more significant in the oxidation of frans-decaline (4 96), indicating that products arising from methylene oxidation are largely dominant. The rationale for this behavior lies on the steric demand exerted by the methyl group in the a-position of the pyridine, which remains in close proximity to the iron site. This fact favors preferential oxidation at the spatially more accessible methylenic sites in contrast to the more embedded tertiary C-H bonds. More importantly, this could be applied to divert regioselectivity in the C-H oxidation of (-F)-neomenthyl esters (Scheme 29). Whereas [Fe(OTf)2(pdp)j offered poor discrimination between secondary and tertiary C-H bonds, [Fe(OTf)2((5,5,/ )-mcpp)] and [Fe(OTf)2( Pytacn)] were found to be complementary, the former... 

For the regioselectivity similar rules as for the ester pyrolysis do apply. With simple, alkylsubstituted amine oxides a statistical mixture of regioisomeric olefins is obtained. On the other hand with cycloalkyl amine oxides the regioselectivity is determined by the ability to pass through a planar, five-membered transition state. This has been demonstrated for the elimination reaction of menthyl dimethylamine oxide 10 and neomenthyl dimethylamine oxide 11 ... 

The enantiodifferentiating photoisomerization of achiral ethyl ester 20a was performed in NaY zeolite supercages, which were chirally modified with ephedrine, pseudoephedrine, norephedrine, diethyl tartrate, alaninol, phenylalani-nol, valinol, menthol, and bomylamine, to give trans product 21a in relatively low ees modification with diethyl tartrate led to the highest ee of 12%, while the other inductors afforded ees less than 5%. They also investigated the diastereodifferentiating photoisomerization of chiral esters 20b-d in unmodified zeolites. Photoirradiation of menthyl, neomenthyl, isomenthyl, fenchyl, isopinocamphyl, and 2-methylbutyl 23,33-diphenyl-la-cyclopropanecarboxylates 20b-d in LiY,... 

Thioureas of amino acids have been prepared from (—)-l,7-dimethyl-7-norbomyl isothiocyanate (59) or (-h )-neomenthyl isothiocyanate (60) and separated as their methyl and t-butyldimethylsilyl esters by normal phase liquid chromatography [9]. The derivatives were unsuitable for reversed phase liquid chromatography, and no separation was achieved for either the free acid or the methyl ester. Derivatives from 2,3,4,6-tetra-O-... 

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