4-Methoxy-3-cyclohexen

Lycoramine. Lycoramine (300)[79] synthesised by Parker et al [80] utilised an intramolecular 5-exo radical addition to an appropriately located double bond to generate the quaternary carbon centre (Scheme 46). The starting material, the silyloxybromo ketone 301, was secured initially as a mixture of isomers from 4-methoxy-3-cyclohexen-l-ol (302) by silylation to 303 followed by bromination. On standing or in contact with silica, the mixture was converted essentially into 304. The overwhelming preference for the substance 301 to exist... 

NH4CI added to a soln. of 9.9 g. 4-methoxy-3-cyclohexene-1-carboxaldehyde (prepn. s. 750) in methanol, and refluxed 1.5 hrs. after abatement of the exothermic reaction 4-oxocyclohexanecarboxaldehyde dimethyl acetal. Y 85%.—In small scale prepn., the water produced is sufficient to hydrolyze the enolether. In larger scale prepn., water is added after the acetal formation has proceeded, and the mixture is stirred for 1.5 hrs. J. I. DeGraw, L. Goodman, and B.R. Baker, J. Org. Ghem. 26, 1156 (1961). 

In a detailed investigation, Turner and coworkers have described the preparation and application of solid-supported cyclohexane-1,3-dione as a so-called capture and release reagent for amide synthesis, as well as its use as a novel scavenger resin [125]. Their report included a three-step synthesis of polymer-bound cyclohexane-1,3-dione (CHD resin, Scheme 7.104) from inexpensive and readily available starting materials. The key step in this reaction was microwave-assisted complete hydrolysis of 3-methoxy-cyclohexen-l-one resin to the desired CHD resin. 

Amino-ethyl)-3-hydroxy-l-methoxy-cyclohexen wird schon in der Kalte durch 20%ige Schwefelsaure unter Hydrolyse der Methoxy-Gruppe zu 7-Oxo-2-aza-bicyclo [3.3. l]nonan cyclisiert3. 

Most concerted 1,4-eliminations have been found to occur with syn stereochemistry. The reaction shown in equation 10.5 (page 635) was found to be more than 99% syn, consistent with the mechanism shown in Figure 10.27. ° In some cases, it appears that 1,4-eliminations occur not by a concerted pathway but by a mechanism with considerable carbanion character. In the gas phase, 1,4-eIimination of methanol from 3-methoxy-cyclohexene was found to occur by a concerted S)m pathway with a weak base (such as fluoride), but by a nonstereoselecHve carbanion pathway with a stronger base (such as amide or hydroxide). ... 

Diacetoxylation of various conjugated dienes including cyclic dienes has been extensively studied. 1,3-Cyclohexadiene was converted into a mixture of isomeric l,4-diacetoxy-2-cyclohexenes of unknown stereochemistry[303]. The stereoselective Pd-catalyzed 1,4-diacetoxylation of dienes is carried out in AcOH in the presence of LiOAc and /or LiCI and beiizoquinone[304.305]. In the presence of acetate ion and in the absence of chloride ion, /rau.v-diacetox-ylation occurs, whereas addition of a catalytic amount of LiCl changes the stereochemistry to cis addition. The coordination of a chloride ion to Pd makes the cis migration of the acetate from Pd impossible. From 1,3-cyclohexadiene, trans- and ci j-l,4-diacetoxy-2-cyclohexenes (346 and 347) can be prepared stereoselectively. For the 6-substituted 1,3-cycloheptadiene 348, a high diaster-eoselectivity is observed. The stereoselective cij-diacetoxylation of 5-carbo-methoxy-1,3-cyclohexadiene (349) has been applied to the synthesis of dl-shikimic acid (350). 

The relative configuration of the diastcrcomers obtained on reaction of A-benzoyl a-methoxy-glycine methyl ester and various activated cyclohexenes is dependent on the cyclohexene substituent88. Whereas the boron trifiuoride catalyzed reaction with l-(4-morpholinyl)cyclohexene gives predominantly the awt/ -isomer, the. vrn-isomcr is predominantly formed in the titan-ium(IV) chloride catalyzed reaction with trimethylsilyloxycyclohexene. These results arc explained by a cyclic and an acyclic transition state, respectively. As expected, acetoxycyclohex-ene is less reactive. 

Benzene, [(l-cyclohexen-l-yl)methoxy-methyl]- [10084-62-5], 105 Benzene, (cyclohexyltdenemethyl)- [1608-31-7], 105... 

Hydroxy-9-methoxy-3,7-dimethyl-1 - [2,6,6-trimethyl-cyclohexen-( 1 )-yl ]-nonatrien-(I,4,6)... 

The Suzuki coupling of 2-iodo-2-cyclohexen-1-one and 4-methoxy-phenylboronic acid is achieved using silver(l) oxide as a suspension in aqueous THF as the base. Unlike earlier reports,15-17 in which up to 6 equiv of Ag2mild conditions, rapid conversion can be achieved at room temperature for a large variety of sensitively functionalized partners in near quantitative yields (see Table).18... 

Vinyl ethers were reductively cleaved by lithium, sodium or potassium in liquid ammonia especially in the absence of alcohols (except terf-butyl alcohol) A mixture of l-methoxy-1,3- and l-methoxy-l,4-cyclohexadiene gave in this way first methoxycyclohexene and, on further reduction, cyclohexene Reductive cleavage of a-alkoxytetrahydrofurans and pyrans will be discussed in the chapter on acetals (p. 104). 

Cycloadditions give better efficiency and stereocontrol for ring formation. A high regioselectivity (95 5) for the cycloaddition of dichloroketene to a cyclohexene en route to synthetic eriolanin [164] has been observed. It appears that the allylic methoxy group play a dominant role. Note that the proximal sp2-carbon is a donor by virtue of its 1,3-relationship with the oxygen function. 

DIMETHYL-l,3-CYCLOHEXANE-DIONE] IRON, 57, 16 TRICARBONYL[(l, 2,3,4,5-r))-2-METH-OXY-2.4-CYCLOHEXADIFN-1-YL]-IRON( l+)HEXAFLUOROPHOS-PHATE(l-), 57, 107 Tricarbonyl [(1,2,3,4,5-r) )-l-mcthoxy-2,4 cyclohexadien-l-yl] iron(l+)tetra-fluoroborate(2-), 57, 1 09 Tricarbonyl [(1,2,3,4,5-r))-2-methoxy-2,4-cyclohexadien-l-yl] iron(l+)tetra-fluoroborate(l-), 57, 109 3-Tnchloroacetamido- 1-cyclohexene, 58,... 

Cyclocondensation of cis- and trans-2-amino-4-cyclohexene-l-carboxylic acid with 2-methoxy-3,4,5,6-tetrahydropyrimidine in boiling chlorobenzene for 6 h gave ds-4a,lla-H- and trani-4a,lla-H-l,4,4a,6,7,8,9,lla-octahydro-1 l//-pyrido[2,l-6]quinazolin-l 1-ones (75 and 78) (90PHA109). 

Under the standard reaction conditions (no sodium acetate), the cyclic olefins tested afforded predominantly diesters with the exception of cyclohexene which gave a low yield of /3-methoxy ester (Table II). In each case, the cycloalkane 1,2- and 1,3-dicarboxylic esters obtained were the cis isomers. The relative rates of diester formation show the... 

Previous work has shown that the electronic characteristics of the benzene substituent in triarylphosphine chlororhodium complexes have a marked influence on the rate of olefin hydrogenation catalyzed by these compounds. Thus, in the hydrogenation of cyclohexene using L3RhCl the rate decreased as L = tri-p-methoxyphenylphosphine > triphenylphosphine > tri-p-fluorophenylphosphine (14). In the hydrogenation of 1-hexene with catalysts prepared by treating dicyclooctene rhodium chloride with 2.2-2.5 equivalents of substituted triarylphosphines, the substituent effect on the rate was p-methoxy > p-methyl >> p-chloro (15). No mention could be found of any product stereochemistry studies using this type of catalyst. 

Groves et al. found that a simple heme-iodosobenzene system mimics the enzymic reactions.127 Cyclohexane and cyclohexene are oxidized to cyclohexanol and a mixture of cyclohexene oxide and cyclohexenol respectively by this system. Using meso-tetrakis-a,/J,a,/J-(o-acylamidophenyl)por-phinatoiron(III) chloride where the acyl group is (i )-2-phenylpropionyl or (S)-2 -methoxy-carbonyl-l,T-binaphthyl-2-carbonyl, optically active styrene oxides are obtained in 51% e.e. The Fe(TPP)Cl-PhIO system can also oxygenate arenes to arene oxides.128 Based on the following observations, mechanisms involving O—Felv(Por) t as the active species have been proposed (Scheme 30).127... 

The photoaddition of nitrobenzene to cyclohexene at — 70° results in the formation of the first reported 1,3,2-dioxazole [Eq. (93)].342 A novel dimerization is observed in the photolysis of 2-methoxy-6-phenyltropone (318) to the furan derivative (319) in low yield.343 This is regarded as the first 1,8-dipolar photoaddition to be observed. 

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