2-Cyclohexenols

Hydroxymethylmethyldiazirine (209 unprotonated) formed propionaldehyde as the sole product by thermal nitrogen extrusion 4-hydroxy-l,2-diazaspiro[2.5]oct-l-ene (218) formed a mixture of cyclohexanone (73%), cyclohexenol (21%) and cyclohexene oxide (5%). Thermal decomposition of difluorodiazirine (219) was investigated intensively. In this case there is no intramolecular stabilization possible. On heating for three hours to 165-180 °C hexafluorocyclopropane and tetrafluoroethylene were formed together with perfluorofor-maldazine 64JHC59). 

The solvolysis of the tosylate of 3-cyclohexenol has been studied in several solvents. The rate of solvolysis is not very solvent-sensitive, being within a factor of 5 for all solvents. The product distribution is solvent-sensitive, however, as shown below. 

Stork and Kahne 108) have demonstrated remarkable stereochemical control in the hydrogenation of a series of cyclohexenols containing allylic... 

A high endo selectivity is observed in the reaction of (phenylsulfonyl)allene (112) with furan (157) (equation 113)108. The endo adduct 158 can be readily transformed into highly substituted cyclohexenol 160 upon treatment with n-butyllithium after hydrogenation of the ring double bond (equation 114)108. 

R = Me, R = H) with cyclohexenol in the presence of F ion followed by NaOCl oxidation gave the tricyclic ether 61 in 65% yield (Scheme 9) [29]. The use of propargyl alcohol and propargyl thiol led, via the acetylenic oximes, to fused tetrahydrofuranoisoxazoles 62 a and 62 b, and tetrahydrothiopheno[3,4-c]isoxa-zole 62 c, respectively. Reaction of l-butyn-4-ol with 0-trimethylsilyl a-bro-moaldoxime 52e (R = R = Me) led to the tetrahydropyranoisoxazole 62 d. 

In a new version of the Simmons-Smith reaction allyl or aUenic alcohols such as cyclohexenol are converted by Sm/CH2l2/Me3SiCl 14 in THF at -78°C into syn cyclopropanols such as 2135 [63] (Scheme 13.17). 

Polar substituents can exert a directing effect. Cyclohexenol, for example, gives high regioselectivity but low stereoselectivity.28 This indicates that some factor other than hydroxy coordination is involved. 

Scheme 5.15 DKR of cyclohexenyl acetate to give a (-)-cyclohexenol with P. fluorescens lipase immobilized in an Si02 sol-gel matrix [62].

The more hindered alkoxide Ti(OiPr)4 was used as the precursor complex with surface silanols of an amorphous silica support this reaction is reported to lead to the same environment of Ti as in TS-1, but only when the reaction is carried in cyclohexanol as the solvent. Epoxidation of octene, cyclohexenol, and norbornene with FI202 in phenylethanol leads to 95-98% epoxide selectivity.147... 

A novel procedure for the synthesis of an indole skeleton 81 was developed by Mori s group (Scheme 13).16e,16f Enantioselective allylic amination of 78 with A-sulfonated < r/ < -bromoaniline 79 followed by Heck cyclization of 80 provided chiral indoline 81. The treatment of a cyclohexenol derivative 78 with 79 in the presence of Pd2(dba)3-GHGl3 and ( )-BINAPO gave compound 80 with 84% ee in 75% yield. Total syntheses of (—)-tubifoline, (—)-dehydrotubifoline, and (—)-strychnine were achieved from compound 80. 

Lautens and Rovis showed that the rate of addition of the reducing agent DIBAL had a significant effect on the reactions. Fast addition of the DIBAL (addition time to 7 min this raised the ee to 82% (entry 2, Table 11). The optimal addition time was found to be 1 h which gave the cyclohexenol 121 with 97% ee (entry 3, Table 11). It was possible to reduce the amount of catalyst to l-2mol%. 

The conditions for the reaction were sufficiently mild so that a broad range of substituents was tolerated. However, steric congestion close to the reacting olefin resulted in a decrease in enantioselectivity giving the cyclohexenol 123 in 81% yield and 84% ee (Table 12). 

Ru complex and (CH3)3COK [(S, R)-34B] is also an excellent catalyst for hydrogenation of the cyclic enone [111]. The allylic alcohol product is a useful intermediate for the synthesis of carotenoid-derived odorants and other bioactive ter-penes. Hydrogenation of 2-cyclohexenone in the presence of the (S,S)-DIOP-Ir catalyst gives (R)-2-cyclohexenol in 25% ee (Fig. 32.43) [137]. 

Besides the silyl enolate-mediated aldol reactions, organotin(IY) enolates are also versatile nucleophiles toward various aldehydes in the absence or presence of Lewis acid.60 However, this reaction requires a stoichiometric amount of the toxic trialkyl tin compound, which may limit its application. Yanagisawa et al.61 found that in the presence of one equivalent of methanol, the aldol reaction of an aldehyde with a cyclohexenol trichloroacetate proceeds readily at 20°C, providing the aldol product with more than 70% yield. They thus carried out the asymmetric version of this reaction using a BINAP silver(I) complex as chiral catalyst (Scheme 3-34). As shown in Table 3-8, the Sn(IY)-mediated aldol reaction results in a good diastereoselectivity (,anti/syn ratio) and also high enantioselectivity for the major component. 

BINAP Ru catalyst and (lR,25 )-ephedrine (Scheme 8-53). This result is similar to that obtained when catalyzed by pure (R)-BINAP. In pure (R)-BINAP complex-catalyzed hydrogenation, (S )-2-cyclohexenol can also be obtained with over 95% ee. This means that in the presence of (R)-BINAP-Ru catalyst, (R)-cyclohexenol is hydrogenated much faster than its (S )-enantiomer. When ephedrine is present, (R)-BINAP-Ru will be selectively deactivated, and the action of (S -BINAP-Ru leads to the selective hydrogenation of (S)-2-cyclohexenol, leaving the intact (R)-2-cyclohexenol in high ee. 

Cyclohexene, bromination of, 47, 32 reaction with 1-butyl perbenzoate and cuprous bromide, 48,18 2-Cyclohexenol, 46, 32 2-Cyclohexen-I-ol, benzoate, 48, 18 2-Cyclohexenone, 45, 32 Cydohexyl allophanamide, 45, 72 Cyclohexylamine, 45, 85 reaction with 1-butyl hypochlorite, 46, 16... 

Tricyclic heptanones.1 The reaction of 1 with CHjMgBr and then with lithium cyclohexenolate results in 2 and the tricyclic product 3. The minor product 2 can be converted into 3 in high yield by further reaction with CH3MgBr and lithium... 

Using methods developed by Sharpless (68), Reich (69), and others, the optically active 4,4-dimethyl-2-cyclohexenol is prepared in excellent yield from the corresponding chiral selenide (eq. [19]). The (S)-4,4-dimethyl-3-p-methylphenylselenocyclohexanone, [a] 42.1° (e.e. 39%), was reduced with sodium borohydride to the (one) diastereomeric alcohol, [a] 11.0°, in quantitative yield and converted to the allylic alcohol, [a] — 17.7°, with an e.e. of 40%. 

The rate of dehydration of the cis diol was about fifty times slower than that of the trans diol and the product of the reaction consisted mainly of cyclohexenol. The 1,4-epoxycyclohexane formed in the reaction was formed after a prior epimerization of the cis to the trans diol this was demonstrated by means of tritium tracer technique. When irons-1,4-cyclohexanediol was dissolved in ieri-butyl alcohol-T having the hydroxyl hydrogen marked with tritium (C4H,OT) the 1,4-epoxycyclohexane produced in this reaction had a very low tritium content. A similar reaction carried out with cis-1,4-cyclohexanediol produced a highly tritiated 1,4-epoxycyclohexane. The insertion of tritium in the 1,4-epoxycyclohexane produced from the cis diol can be explained as follows ... 

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