1- Methylcyclohexene, synthesis

Whatprodiictfs) would you expect from the reaction of l-methylcyclohexene with NBS Would you use this reaction as part of a synthesis ... 

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). 

The RCM of (+)-/l-citronellene (38, 2,6-dimethylocta-2,7-diene) in toluene (0.75 M), induced by 8, proceeds quantitatively at 20 °C to yield isomerically pure (S)-3-methylcyclopentene (39) see equation 29226. The same result can be achieved with rrans-WOCl2(OC6H3-Br2-2,6)2/Et4Pb as catalyst78. This is a remarkable improvement on the previous, very difficult synthesis of this compound. In concentrated solution in toluene (5 m), 39 undergoes ROMP when initiated by 8 at — 30 °C226. (S)-4-methylcyclohexene can be made in a similar way, as can 3,3-dimethylcyclohexene and 2-methylcyclohexene78. 

Optical resolution of some hydrocarbonds and halogeno compounds by inclusion complexation with the chiral host (9a) has been accomplished.11,12 Preparation of optically active hydrocarbons is not easy and only a few example of the preparation of optically active hydrocarbons have been reported. For example, optically active 3-phenylcyclohexene has been derived from tartaric acid through eight synthetic steps.11 Although one-step synthesis of optically active 3-methylcyclohexene from 2-cyclo- hexanol by the Grignard reaction using chiral nickel complex as a catalyst has been reported, the enantiomeric purity of the product is low, 15.9%.11 In this section, much more fruitful results by our inclusion method are shown. 

This synthesis requires the conversion of an alcohol to an alkyl bromide with the bromine atom at the neighboring carbon atom. This is the anti-Markovnikov product, which could be formed by the radical-catalyzed addition of HBr to 1-methylcyclohexene. 

Ssmple Probl6m 26.1 Devise a synthesis of 1 -methylcyclohexene from 1 -bromocyclohexene and CH3I. 

The previously unknown (+ )-(lS,2S,4R)-isodihydrocarveol (157) has been made from (+ )-limonene epoxide (158) as a component of a mixture of isomers, either with lithium in ethylamine or with the stoicheiometric amount of lithium aluminium hydride. Dihydrocarveol (159) has been synthesized from 4-acetyl-1-methylcyclohexene by conventional means.A method that is said to convert allyl alcohols into the corresponding chlorides without allyl rearrangement has been applied to carveol. The chloride was indeed obtained, but since the rotations of the compounds were not recorded it is unfortunately impossible to draw any conclusions about rearrangement. An ingenious synthesis of pure stereoisomers of carvomenthone-9-carboxylic acids involves a [2 -I- 2]-type cycloaddition of an ynamine to 2-methylcyclohex-5-enone (160). This leads... 

Starting with 1-methylcyclohexene and using any other needed reagents, outline a synthesis of the following deuterium-labeled compound ... 

Problem 9.30. As pointed out in Scheme 9.74, methylenecyclohexane is the minor product of the dehydration of 1-methylcyclohexanol while 1-methylcyclohexene is the major product. Propose a synthesis of the former in which the latter might not be found at aU. 

Devise a synthesis of 1-deutero-l-methylcyclohexane starting from 1-methylcyclohexene. 

On a separate piece of paper) Design a synthesis of each of the following target molecules starting from methylcyclohexene and any noncyclic reagents. 

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