1-Methylcyclohexene, reaction with

The question as to whether enol ether 72, the insertion product derived from diethyl diazomalonate and 1-methoxycyclohexene, has a similar origin or arises from a dipolar intermediate of type 102, has already been discussed (Sect. 2.3.1). Interestingly enough, only one formal C/H insertion product was reported in that case, rather than three as in the reaction with 1-methylcyclohexene. 

In addition to the present method,2 1-amino-1-methylcyclo-hexane has been synthesized by the following procedures Ritter reaction, e.g., with 1-methylcyclohexanol (76%, 67%)3i 4 or 1-methylcyclohexene (35%,) 4 5 Hofmann reaction with 1-methyl-cyclohexanecarboxamide (80% as hydrochloride) 6 reduction of 1-methyl-l-nitrocyclohexane (63%) 6 Schmidt reaction with 1-methylcyclohexanecarboxylic acid (42%).6... 

Figure 11.34 Illustration of the similarity of the double bond of methylcyclohexene with typical steroids or terpenoids and potential reaction products for methylcyclohexene conversion with H202.

Compounds 16 and 19 each deliver the expected six alcohols after reduction of the primarily formed hydroperoxide mixtures as a result of an oxygen attack on the trisubstituted A1 double bonds of these molecules. The ratio of tertiary/secondary hydroperoxides (or alcohols) is about 44 56, as has also been found with 1-methylcyclohexene (30)13S while open-chain olefins such as trimethylethylene (S3), 1,1-dimethyl-2-ethylethylene (id), 2,6-dimethyl-2-octene (39), myrcene (42), / -citronellol (45), linalool (48), and l,l-dimethyl-2-benzylethylene (51) give ratios of tertiary/secondary hydroperoxides between 54 46 and 60 40.104-1 7 7 1 79 The slight deviations from 1 1 ratios in all these cases are probably due to stereochemical rather than electronic effects exerted by the olefins on the reaction with oxygen. 

In this synthesis the geometry of the acyclic double bonds is controlled through their formation as part of the thiane ring. Thiacyclohexanone (711) was converted to 4-thia-l-methylcyclohexene by reaction with methylmagnesium iodide and subsequent dehydration. Metallation of (712) with s-butyllithium and alkylation of the anion with the epoxide (713) gave a tertiary alcohol which was dehydrated to yield (714). A second alkylation of (714) with trails-4-chloro-3-methyl-2-butene 1-oxide (715) completed the carbon skeleton of the Cis juvenile hormone. Reduction of (716) with lithium in ethylamine and then desulfurization with Raney nickel led to trienol (717), a product converted previously to (718). 

Reactions between KCH2SiMe3 and cyclohexene or methylcyclohexene gave white solids formulated as 59 or 60. They were characterized by reaction with CHzO and oxidized with (COCl)2, but no structural data have been reported. Reactions with cyclooctene were similar.45 The role of tertiary amine in the metallation of ethene, n-hexene, and a-pinene has been studied.15... 

The methyl group is introduced by a Grignard reaction with methylmagnesium bromide. Dehydration of the resulting tertiary alcohol produces 1-methylcyclohexene. 

A detailed study of the reactions of trichlorogermane with unsaturated compounds was performed . It became clear that among selected olefins only 1-heptene forms the anti-Markovnikov adduct in the reaction with trichlorogermane. In contrast to the generally accepted opinion, in the reactions with 1-methylcyclohexene (equation 11), styrene (equation 12), 2,3-dimethyl-l-butene (equation 13) and isobutene (equation 14) both regioisomers 4 and 5, 6 and 7, 8 and 9, and 10 and 11 appear in commensurable amounts (together with oligomeric products see later, equation 16). 

Reaction with l-chloro-2-methylcyclohexene (1). This vinyl halide reacts with phenyllithium (5 equiv.) to give the bicyclo[4.1.0]heptane (2) in 90% yield. The paper presents evidence for the intermediacy of the cyclopropene a. Other organo-lithium reagents react in the same way, but yields are lower, 47% in the case of CHjLi. 

The photoaddition of an excess of 1-nitrosopiperidine to 3-methylcyclohexene is diastereo-selective and afforded exclusively rran. -2-methyl-6-(l-piperidinyl)cyclohexanone oxime (4) as a mixture of (E)- and (Z)-isomers. The reaction with Ar-nitrosodimethylamine was less efficient and also produced a small amount (2%) of the (E)-trans-regioisomer the major product was separated and reduced to the corresponding 1,2-diamines 5 with slightly different diastereo-selectivity32. The relative ratio of diastereomeric diamines and the relative stereochemistry of the three substituents in the predominant diamine diastereomer were established by HNMR of the. V-acetyl derivative, while those of the minor diastereomer were proposed from mechanistic considerations. The photoaddition of A -nitrosodimethylamine with 4-fer/-butylcyclohex-ene, however, afforded a mixture of diastereomers and regioisomers21,32. 

High catalytic activities, with turnovers of up to 9(X) cycles min , is displayed in the transfer hydrogenation of a,p-unsaturated ketones, such as benzylideneacetone and chalcone, using 2-propanol and catalytic amounts of [Ir(3,4,7,8-Me4-phen)COD]Cl (phen = 1,10-phenanthroline COD = 1,5-cyclo-octadiene) in a weakly alkaline medium. Other Ir-chelated complexes are also active catalysts in this reaction, with over 95% selectivity for the 1,4-reduction mode. Divalent lanthanide derivatives, such as Sml2 or Ybh in stoichiometric quantities, in THF and t-butyl alcohol or methanol reduce ethyl cinnamate and cinnamic acid to give the saturated derivatives. " Similarly, 3-methylcyclohexenone is reduced to 3-methylcyclohexen-l-ol in 67% yield, but a,p-unsaturated aldehydes are nonselectively reduced with these systems. 

Reduction of epoxides. The reaction of diborane alone with epoxides is complicated. Thus 1,2-butylene oxide requires 48 hrs. and gives a mixture of butanols (96% 2-butanol and 4% 1-butanol) in only 48% yield. The reaction with trisub-stituted epoxides is even more complicated and only trace amounts of simple alcohols are formed. Brown and Yoon1 found that the presence of trace amounts of sodium or lithium borohydride greatly enhances the rate of reaction and modifies the course to give predominantly anti-Markownikov opening of the epoxide ring. Thus 1-methylcyclohexene oxide is reduced mainly to m-2-methylcydohexanol ... 

A similar reaction of (diacetoxyiodo)benzene with alkenes and trimethylsilyl isothiocyanate in dichloromethane affords 1,2-dithiocyanates 540 in moderate yield (Scheme 3.212). Cyclic alkenes, such as cyclohexene and 1-methylcyclohexene, react with this reagent system stereoselectively with the formation of the respective trans-aMuct [598,599],... 

In a reaction resembling halohydrin formation (Section 6.17), vicinal haloethers are prepared from alkenes by reaction with an alcohol in the presence of halogens— usually bromine or iodine. This haleotherification proceeds through a cyclic halonium ion, which reacts with the alcohol. 1-Methylcyclohexene undergoes iodoetherification with ethanol in the presence of iodine to give ran -l-ethoxy-2-iodo-l-methylcyclohexane. 

Similarly, reaction of 2-methylpropene with hydrogen bromide gives only 2-bromo-2-methylpropane, and 1-methylcyclohexene combines with HI to furnish only 1-iodo-l-... 

The purity of the product was determined by the checkers by GLC analysis using the following column and conditions 3-nm by 1.8-m column, 5% free fatty acid phase (FFAP) on acid-washed chromosorb W (60-80 mesh) treated with dimethyldichlorosilane, 90 C (1 min) then 90 to 200 C (15°C per rain). The chromatogram showed a major peak for methyl 2-methyl-l-cyclohexene-l-carboxylate preceded by two minor peaks for methyl 1-cyclohexene-l-carboxylate and l-acetyl-2-methylcyclohexene. The areas of the two impurity peaks were 5-6% and 0.5-2% that of the major peak. The purity of the product seems to depend upon careful temperature control during the reaction. The total amount of the two impurities was 14-21% in runs conducted at about -15 to -20°C or at temperatures below -23°C. 

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