1.2- Dimethylcyclohexene, reaction with

A similar reaction the with rran.v-isomer 3b gave c -3,5-dimethylcyclohexene (4) with very high diastereoselectivity. Accordingly, the stereochemistry of this substitution is anti. Deuterium labeling experiments using the 1-deuterio or 3-deuterio derivative of 3 a showed that the ratio of SN2 /SN2 with lithium dimethylcuprate was about 50 50, while the ratio with lithium cyano(methyl)cupratc was >96 4. 

Cg Aromatic Reactions with Hydrogen. The mild acid nature of the family of aluminophosphate based sieves renders them selective for a number of rearrangements as observed in the reactions of olefins and paraffins described above. This property as well as their apparent low disproportionation activity observed in the alkylation of toluene suggests that they be evaluated as the acid function in bifunctional Cg aromatic isomerization. As described above, cyclo-olefins are most likely involved in the conversion of ethylbenzene to xylenes. Strong acid functions, such as in mordenite, actively isomerize cyclo-olefinic intermediates but also catalyze ring-opening reactions which lead to loss of aromatics. A more selective acid function must still effectively interconvert ethyl cyclohexene to dimethylcyclohexenes but must leave the cyclohexene rings intact. 

Annelation. The reagent reacts with enamines to give fluorinated cyclo-hexenones. Thus the reaction with 2-methyl-1-pyrroUdinopropene (2) gives 6-fluoro-4,4-dimethylcyclohexene-2-one-l (3) in 65% yield. 

What products would you expect from reaction of 4,4-dimethylcyclohexene with NBS ... 

The triethylsilane/trifluoroacetic acid reagent system reduces alkenes to alkanes in poor to excellent yields depending largely on the ability of the alkene to form carbocations upon protonation. Under these conditions the more substituted olefins are reduced in better yields and styrene double bonds are reduced in high yields.127,202,207,221-228 The reduction of 1,2-dimethylcyclohexene with this reagent gives a mixture of cis- and trans- 1,2-dimethylcyclohexane.229 The formation of the trifluoroacetate esters is a side reaction.205,230... 

In comparison, the ratio of 2,4-/l,3-dimethylcyclohexene obtained from m-xylene is close to unity (1.2) and the ratio changes little during the course of the reaction. An initial random distribution should yield equal amounts of these isomeric cycloalkenes and the relative constancy of the ratio is consistent with the fact that, in competition with one another, 1,3- and 2,4-dimethylcyclohexene are reduced at comparable rates. The failure to observe the other postulated dimethylcyclohexenes is to be expected, because none would have substituents attached to the double bond in the cycle. Consequently, because of their expected greater reactivity in competition, their maximum concentration should be no more than a few per cent of the most reactive of the cycloalkenes actually observed in these experiments. 

Very few data are available concerning the stereochemistry of these additions. Hydration of 1,2-dimethylcyclohexene was found to be nonstereoselective.27 In contrast, predominant or exclusive exo-syn addition was shown to take place in the reaction of 2,3-dideuteronorbomene with water and alcohols 28... 

Reaction of 1,2-dimethylcyclohexene with the ethylene glycol acetal of acrolein in methylene chloride in the presence of 25 mol % of BF3.0Et2 at -78 to -10°C for 2 hours gives a 70% yield of the cycloadduct 1 in a formal 2k + 2% intermolecular cycloaddition. All of the evidence for this and related reactions, however, indicates a stepwise mechanism for the formation of 1. 

Diphenylmethane does not undergo cycloaddition reactions on direct excitation in the presence of electron acceptors (Gilbert and Lane, 1981). Reaction only occurs when the radiation is absorbed into the intermolecular charge-transfer band. With maleic anhydride [2 + 2] cycloaddition to one of the phenyl rings of diphenylmethane occurs and then the cyclohexa-1,3-diene so created reacts thermally with a further mole of the anhydride. Benzonitrile forms a number of cycloaddition products (Cantrell, 1977), e.g. with 1,2-dimethylcyclohexene [130], [131] and [132] are formed (Scheme 29). Products... 

The hydrogenation of 1,2-dimethylcyclohexene (17 Pt02, HOAc, 1 atm) yields trans-(19) as well as cis-1,2-dimethylcyclohexane (18), but Ir and Os in t-butyl alcohol are much more selective (equation lb). The addition of hydrogen to (17) competes with isomerization to 1,6-dimethylcyclohexene (20), which not only reacts more rapidly but yields trans (19) as well as the cis product (18) via syn addition of the two hydrogen atoms (equation 17). In the Pt-catalyzed reaction, the intermediate (20) can be observed, although its steady-state concentration remains low (0.21% of the 1,2-isomer 17) because of its... 

The reaction of cyclohexene oxide with LiBr-HMPA in refluxing benzene leads exclusively to cy-clopentanecarbaldehyde, but, like other enolizable aldehydes, the product is not indefinitely stable to the reaction conditions. The rearrangement of 1,2-dimethylcyclohexene oxide, although much slower, gives only the ketone (218) as shown in equation (120). This result is especially difficult to rationalize by any mechanism other than one requiring a bromohydrin intermediate. 

In this reaction the C=C double bond acts as a nucleophile, and in most acyclic or monocyclic molecules oxygen is added with equal facility to the top or bottom face of the alkene. Oxiranes are the most reactive ethers, and are readily susceptible to nucleophilic attack, which results in ring opening. This is in contrast to diethyl ether (ethoxyethane), which is inert even in the presence of, for example, LiAlH4. Likewise, 1,2-dimethylcyclohexene (27) reacts with peroxy acids to give cis-1,2-dimethylcyclohexene oxide (28). 

Catalytic cyclopropanation of alkenes with diazomalonates is sometimes carried out with copper powder, but it appears that copper(I) halide/trialkyl phosphite complexes (for a procedure see Houben-Weyl Vol. E19b, p 1113), bis(acetylacetonato)copper(II), " ° and tet-raacetatodirhodium can be employed more advantageously (Table 13, entries 7-9). For the cyclopropanation of styrene with dicyclohexyl diazomalonate, however, copper(I) triflate was the catalyst of choice, while intramolecular C —H insertion at the cyclohexyl ring took place in the presence of tetraacetatodirhodium. A detailed comparison of copper catalysts for the cyclopropanation of cyclohexene, 1-methyl- and 1,2-dimethylcyclohexene, (Z)- and ( )-hept-2-ene with dimethyl diazomalonate, including competitive reaction pathways such as allylic C-H insertion and carbene dimer formation, is available. The catalyzed interaction between diazomalonic esters and enol ethers leads to cyclopropanes in some cases (e.g. ethoxymethylenecyclohexane to dimethyl 2-ethoxyspiro[2.5]octane-l,l-dicarboxylate ) and to different products in other cases (e.g. 1-methoxycyclohexene, 2-methoxy-3,4-dihydro-2/7-pyran ). This behavior is attributed to the occurence of stabilized dipolar intermediates in these reactions. 

Reaction of dichloroketene with 1,6-dimethylcyclohexene forms 80% of the cyclobu-tanone regio- and stereospecifically (2 90 % de)14. Addition of dichloroketene to 2,7,7-trimeth-ylbicyclo[3.3.0]oct-2-ene gives 60% of the cyclobutanone regio- and stereospecifically15. 

The de Mayo reaction is also observed for oxo-aldehydes these react exclusively from the enol form in which the aldehyde rather than the ketone is enolized. A representative example is the reaction of enolized formylacetone with 1,2-dimethylcyclohexene". 

However, such stereoselectivity is not always observed. For example, hydrogenation of 1,2-dimethylcyclohexene (3) yields trans-4 as well as cis-4, with the product ratio dependent on the metal and the reaction conditions employed 6 19. In contrast to osmium and iridium, which give nearly exclusively the expected co-product, hydrogenation in the presence of platinum results in a higher proportion of the tra .v-product. In the latter case hydrogenation competes with isomerization to 1,6-dimethylcyclohexene. 

Thermal reaction of 1-butene, cis- and trans-2-butene or isobutylene with butadiene yielded 4-ethylcyclohexene, cis- and transA,5-dimethyl-cyclohexene, or 4,4-dimethylcyclohexene, respectively, accompanied by a larger amount of 4-vinylcyclohexene. Rate constants of these respective reactions were calculated by the method above. 

Of particular interest for this review are those reactions of 02 that closely resemble those found in the autoxidation. Since both 02 and R02 react with many olefins to form hydroperoxides, some basis for distinguishing between these reactants can be important in understanding the detailed mechanism of oxidation of a specific compound, particularly in photooxidations where both type I and II processes can occur. Many simple substituted olefins give very similar mixtures of hydroperoxides by the two pathways however, certain structural units do give markedly different hydroperoxides from R02 and 02 and are useful as criteria for mechanism. Examples are 1,2-dimethylcyclohexene [190]... 

When 1,2-dimethylcyclohexene (below) is allowed to react with hydrogen in the presence of a platinum catalyst, the product of the reaction is a cycloalkane that has a melting point of—50 °C and a boiling point of 130 °C (at 760 torr). (a) What is the stmcture of the product of this reaction (b) Consult an appropriate resource (such as the web or a CRC handbook) and tell which stereoisomer it is. 

Among other group transfer reactions, the reduction of 1,2-dimethylcyclohexene with 9,10-dihydronaphthalene is used frequently [4]. 

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