Reagents cyclohexene

Moreau and his co-workers showed that the higher alkylating reagent, cyclohexene or cyclohexyl bromide, gave p, 3-dicyclohexylnaphthalenes selectively over HY.79 81 However, the 2,6-/2,7- ratio was almost unity. 

Table 10.1 Cyclohexenb vs. Benzene Reagent Cyclohexene gives Benzene gives...

Chlorination. Ziegler et al.1 reported one instance of allylic chlorination with the reagent cyclohexene - 3-chlorocyclohexene (29.2% yield). 

A polymeric form of the reagent from hydrogen fluoride and poly(4-vinylpyndine) is especially easy to handle [I0 Other tertiary amines can also be employed [II], and a two-phase mixture of hydrogen fluoride-melamine-pentane hydrofluorinates cyclohexene to fluorocyclohexane m 98% yield [12]... 

Reagent combinations lor additions of the halogen fluorides to cyclohexene to form trans 1 halo 2 fluorocyclohcxane (equation 1) are shown in Table 1... 

It should be pointed out that the mono-, di-, and tribromo derivatives of the reagent all react considerably more rapidly than the trichloro reagent. For example, the tribromo compound reacts with cyclohexene in about 2 hours, while the trichloro compound requires 36 to 48 hours (7),... 

The conjugate addition of medium-order cuprate reagents Li2Cu3Bu5 to 2-cyclohexen-l-one in the presence of 2 equivalents of (4S,5/ )-2-dimethylamino-3-isopropyl-4-methyl-5-... 

Few racemic alkyl p-tolyl sulphoxides were prepared in rather low yields (16—40%) by the reaction of Grignard reagents with mixed anhydrides 108, 109 and compound HO formed in situ from p-toluenesulphinic acid and 3-phthalimidoxy-l,2-benzoisothiazole 1, 1-dioxide167 (equation 59). The mixed anhydrides 109 or 110 when reacted with cyclopen-tene and cyclohexene enamines 111 gave the corresponding a-ketocycloalkyl sulphoxides 112 in low yields (10-41%) along with small amounts of several by-products such as disulphides and thiosulphonates167 (equation 60). 

Reduction of aromatic rings with lithium or calcium " in amines (instead of ammonia—called Benkeser reduction) proceeds further and cyclohexenes are obtained. It is thus possible to reduce a benzene ring, by proper choice of reagent, so that one, two, or all three double bonds are reduced. Lithium triethylborohy-dride (LiBEtsH) has also been used, to reduce pyridine derivatives to piperidine derivatives." ... 

The preparation of Pans-1,2-cyclohexanediol by oxidation of cyclohexene with peroxyformic acid and subsequent hydrolysis of the diol monoformate has been described, and other methods for the preparation of both cis- and trans-l,2-cyclohexanediols were cited. Subsequently the trans diol has been prepared by oxidation of cyclohexene with various peroxy acids, with hydrogen peroxide and selenium dioxide, and with iodine and silver acetate by the Prevost reaction. Alternative methods for preparing the trans isomer are hydroboration of various enol derivatives of cyclohexanone and reduction of Pans-2-cyclohexen-l-ol epoxide with lithium aluminum hydride. cis-1,2-Cyclohexanediol has been prepared by cis hydroxylation of cyclohexene with various reagents or catalysts derived from osmium tetroxide, by solvolysis of Pans-2-halocyclohexanol esters in a manner similar to the Woodward-Prevost reaction, by reduction of cis-2-cyclohexen-l-ol epoxide with lithium aluminum hydride, and by oxymercuration of 2-cyclohexen-l-ol with mercury(II) trifluoro-acetate in the presence of ehloral and subsequent reduction. ... 

Cyclohexene was purchased from BDH Chemicals Ltd., Poole, England, by the submitters and used without purification. This reagent was purchased by the checkers from Fluka AG, Buchs, Switzerland, and distilled before use. 

R = H, Alkyl, R = H, Alkyl, Allyl, c-Alkenyl Reagent = EtgSiH, MegAl, TMS-allyl, 3-TMS-Cyclohexen (-penten) Lewis acid = TiCl4, SnCl4, SnBr4, TfOH Scheme 13 (Table 3)... 

Improvement in the catalyst activities and enantioselectivities was realised by the development of the chiral, bidentate alkoxy-functionalised imidazolium and imidazolidinium pro-ligands (134 and 136). 134, after deprotonation, was used to prepare the well-defined complex 135. Both 136 in the presence of BuLi and Cu(OTf)2 or 135 without any additional co-reagents were efficient catalysts in the asymmetric 1,4 addition of dialky Izincs and Grignards to cyclohexen-2-one giving higher ee (83% at rt and 51% at -30°C, respectively) [107, 108]. 

Show how by using regioselective enolate chemistry and organoselenium reagents, you could convert 2-phenylcyclohexanone to either 2-phenyl-2-cyclohexen-l-one or 6-phenyl-2-cyclohexen-l-one. 

Based on this information the preparation of enone was examined from the unhalogenated (VIII)(X=H). Deprotonation can be performed with n-butyl lithium in THF at 0-5 °C followed by treatment with 3-ethoxy cyclohexen-l-one, followed by an acid quench provides the same enone (XI). This deprotonation also avoids the cryogenic conditions required to prepare enone (XI) when the bromo analog is used. Pyridinium tribromide used for aromatization of enone (XI) to biaryl phenol (X) is an inexpensive reagents ( 80/kg). 

This reaction is extended to the intramolecular ring closure of the intermediate radical 224 with olefinic or trimethylsilylacetylenic side chains [121]. Cu(BF4)2 is also effective as an oxidant (Scheme 89) [122]. Conjugate addition of Grignard reagents to 2-eyclopenten-l-one followed by cyclopropanation of the resulting silyl enol ethers gives the substituted cyclopropyl silyl ethers, which are oxidized to 4-substituted-2-cyclohexen-l-ones according to the above-mentioned method [123]. (Scheme 88 and 89)... 

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. 

The participation of (3-metaloxy metal species in this context was first discussed by Kochi, Singleton, and Andrews in 1968 [7] in relation to their deoxygenation of styrene and cyclohexene oxide by chromium(II) reagents, as shown in Scheme 12.2. 

Cyclohexene The commercially available reagent was washed with aqueous solution of ferrous sulfate, dried with anhydrous sodium sulfate and distilled(bp.83.0°C). The distilled cyclohexene was passed through an alumina column. This process of purification was repeated three times. 

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