Cyclohexanol l-

Padhi, S.K., Kaluzna, I.A., Buisson, D. et al. (2007) Reductions of cyclic beta-keto esters by individual Saccharomyces cerevisiae dehydrogenases and a chemo-enzymatic route to (lR,2S)-2-methyl-l-cyclohexanol. Tetrahedron Asymmetry, 18 (18), 2133-2138. 

The reverse micelles stabilized by SDS retard the autoxidation of ethylbenzene [27]. It was proved that the SDS micelles catalyze hydroperoxide decomposition without the formation of free radicals. The introduction of cyclohexanol and cyclohexanone in the system decreases the rate of hydroperoxide decay (ethylbenzene, 363 K, [SDS] = 10 3mol L [cyclohexanol] =0.03 mol L-1, and [cyclohexanone] = 0.01 mol L 1 [27]). Such an effect proves that the decay of MePhCHOOH proceeds in the layer of polar molecules surrounding the micelle. The addition of alcohol or ketone lowers the hydroperoxide concentration in such a layer and, therefore, retards hydroperoxide decomposition. The surfactant AOT apparently creates such a layer around water moleculesthat is very thick and creates difficulties for the penetration of hydroperoxide molecules close to polar water. The phenomenology of micellar catalysis is close to that of heterogeneous catalysis and inhibition (see Chapters 10 and 20). 

The ring closures of cis- and fra/t5-2-aminomethyl-l-cyclohexanols and frani-2-hydroxymethyl-l-cyclohexylamine with aromatic aldehydes are highly diastereoselective. After recrystallization of the reaction products, the presence of single diastereomers 31-33 was observed [72ACH(73)81 80ACH(105)293, 800MR204 87JOC3821],... 

The cyclizations of cis- and lrans-2-hydroxymethyl-l-cyclohexylamine and cis- and lram-2-aminomethyl-l-cyclohexanol with 4-nitrobenzaldehyde have been studied by means of H NMR spectroscopy in CDCI3 solution (90ACSA364 91T2229). The time-dependent spectra confirmed that the reactions of all these amino alcohols proceeded via Schiff bases. With the exception of cis-2-hydroxymethyl-l-cyclohexylamine, the thermodynamically more stable perhydrobenzoxazine epimer is also the kinetically favored product. In the former case, from amino alcohol 21 (R = H), the Schiff base 37 with N-outside predominant conformation is formed first due to kinetic control, the less stable epimeric ring form 38 is obtained with N-outside predominant conformation. The thermodynamically controlled product 33 is formed subsequently, via the less stable open-chain form 37, in a slow equilibration process (90ACSA364). 

Pankova and Tichy prepared all four stereoisomeric 4-rerr-butyl-2-aminomethyl-l-cyclohexanols and cyclized them with ethyl benzimidate to hexahydro-l,3-benzoxazines 158-161 (74CCC1447). From the A-acyl O-mesylate derivatives 162 and 163 on thermal cyclization or thionyl chloride treatment, ring closure occurred with inversion and resulted in 158 and 159 (74CCC1447). 

In the reactions of cis- and rrans-2-aminomethyl-l-cyclohexanol or -1-cycloheptanol or cis- and trans-2-hydroxymethyl-l-cyclohexylamine or -1-cycloheptylamine with ethyl 4-chlorobenzimidate, the stereo- and regio-isomeric derivatives and homologs 164 and 165 were prepared (79T799). The amidine intermediate 166 of the benzimidate ring closure was also... 

The ring-chain tautomerism of tetrahydro-l,3-oxazines is very sensitive to the stability differences, the substituents and the ring-fusion effect (Section IV,A). It also reveals a considerable stability difference in favor of the cis isomers. In the reactions of the cis- and trans-2-amino-l-cyclohexanols, as compared with the hydrindane analog systems, where the heteroatoms form an oxazolidine ring cis- or tra 5-fused with cyclohexane, the corresponding stability differences were again found to be in favor of the cis isomer (93JOC1967). 

When cyclohexene is oxidized with oxygen on a Co-zeolite, the major product is cyclohexenyl hydroperoxide together with minor amounts of 1,2-epoxycyclohexane and 2,3-epoxy-l-cyclohexanol [45]. However a combination of Co-zeolite with V0(acac)2 and Ho(CO)g (6/1/1) increases the conversion strongly and the epoxides dominate in the product mixture. 

BARDHAN-SENGUPTA SYNTHESIS. Phosphorus pentoxide and other powerful dehydrating agents act upon 2-beta-phenethyl-l-cyclohexanol to form oclahydrophenanlhrene compounds. 

A sterically demanding PhMe2Si group at the C-3 position of 1-cyclohexanone derivatives affects a highly stereoselective reduction of the C-l carbonyl group by NaBI-L in methanol187. The 3-silyl-l-cyclohexanol product holds a cis configuration. 

The 4-exo cyclization of open-chain substrates 63 proceeds in trans-fashion with moderate to excellent selectivity (trans/cis = 77/23 > 99/1 )90. The trans selectivity is dependent on the substitution pattern of R2, R3 and R4. The reactions giving trans-l-aza-2-silacyclobutanes 65 have been applied to the stereoselective syntheses of syn-amino alcohols 66 via the Tamao oxidation as exemplified by the reaction of 63d (R = HMe2Si), affording 66d (76% overall yield in 4 steps, syn/anti = > 99/1) via 65d (trans/cis = > 99/1) in equation 2690. In the case of 3-iV-disilylamino-l-cyclohexene 63f (R = HMe2Si), however, cis-l-aza-2-silacyclobutane 65f is formed exclusively, that is converted to ds-2-amino-l-cyclohexanol (66f) (equation 27)90. 

BBN effects the hydration of the C=C double bond of 1-methylcyclohexene according to Figure 3.25 in such a way that after the oxidative workup, racemic 2-methyl-l-cyclohexanol is obtained. This brings up the question Is an enantioselective H20 addition to the same alkene possible The answer is yes, but only with the help of reagent control of stereoselectivity (cf. Section 3.4.2). 

With NBS in aqueous DMSO, cyclohexene gives racemic /ra/ -2-bromo-1 -cyclohexanol. This stereochemical result means that we have a Irans-addition. In the analogous bromohydrin formation from 3,3-dimethylcyclohexene, the analogous dimethylated 2-bromo-l-cyclohexanol is also produced /ra/rv-selectively as well as regioselectively (Figure 3.43). In the bromo-nium ion intermediate, the H20 molecule does not react at the hindered neopentyl center. This is as expected from the rules for SN2 reactivity (Section 2.4.4), and results in high regioselec-tivity. 

Preparative Methods The title reagent is prepared by reaction of (IR, 2S)-2-phenyl-l-cyclohexanol with excess phosgene in the presence of quinoline to afford a chloroformate which is treated directly with hydrazine monohydrate (0.5 equiv) to afford di-(—)-(IR, 25)-2-phenyl- 1-cyclohexyl diazanedicarboxy-late. Oxidation of the diazanedicarboxylate to the diazenedicarboxylate is then readily effected using N-bromosuccinimide and pyridine (eq 1). 

Gore [30] has found a strong temperature and solvent effect on the reaction of methylmagnesium iodide with ethynyl-l-cyclohexanol. Indeed, the 8N2-coupled compound was obtained as the major product when the reaction was performed in THF under reflux (8n2/8n2 = 95 5), whereas the 8n2 product (allenic derivative) was obtained in ether at low temperature (8 278 2 = 40 60 at 0°C, and 0 100 at — lO C). 

Formation of octahydrophenanthrene derivatives by cyclodehydration of derivatives of 2-((3-phen-ethyl)-l-cyclohexanol and consequent dehydration to phenanthrenes with selenium. 

Pd(OAc)2 (47.35 % Pd) was purchased from Degussa. The compounds 4-iodo-toluene, n-butyllithium (1.6 M in hexane), 3-methyl-l-pentyn-3-ol, 2-butyne-l,4-diol, phenylacetylene, diphenylacetylene, 1-ethynyl-l-cyclohexanol and 2-methyl-... 

Isomerization of ethynylcarbinols. Rupe12 first observed that ethynylcarbinols when refluxed in formic acid (90%) are isomerized to unsaturated carbonyl compounds, which he considered to be aldehydes. Chanley13 later investigated the reaction in detail and found that the predominant product is an a,/ -unsaturated ketone. Thus 1-ethynyl-l-cyclohexanol (1) is converted mainly into 1-acetyl-l-cyclohexene (2), with onLy traces of (3) being formed. 

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