Octanone, hydrogenation

In the hydrogenation of MAA and the 2-alkanones, the pH of the modification solution had a significant influence on e.d. ability of the catalyst [8,9], because it changed the posture of the adsorbed modification reagents [8]. The pH dependence of the modification solution on e.d. ability in the 3-octanone hydrogenation revealed that a pH of 3.2-3.5 gave the maximum e.d. 

The e.d.a s for the 2-octanone hydrogenation with various MNi s are listed in Table 8. The best catalyst for the MAA hydrogenation always brings about the best e.d.a. in the alkanone reaction. This proved that the MAA and 2-alkanone hydrogenation occur in the same E-region of the catalyst. 

A solution of 50 g of 1 -azabicyclo [2.2.2] -3-octanone hydrochloride in 200 cc of water was hydrogenated at room temperature and 50 atm pressure with 1 g of platinum oxide as catalyst. After the calculated amount of hydrogen had been absorbed, the mixture was filtered and concentrated in vacuo to dryness. The residual product was recrystallized from a mixture of methanol and acetone and formed prisms melting above 300°C. It was identified as 1 -ezabicy-clo[2.2.2] -3-octanol hydrochloride. 

The results of the series of reactions shown in eq. 2 are listed in Table 1 together with our early reported data on the hydrogenation of 2-octanone (Z) [4]. The hydrogenation on all substrates proceeded smoothly and gave the corresponding chiral secondary alcohol. In the case of 3, 4, S, and 6, some amounts of lactone were produced as by-product. From this study, quite interesting stereochemical behavior... 

Table 1. Enantioface-Differentiating Hydrogenation of Various Keto Esters and 2-Octanone...

The Ni-tartaric acid system was discovered by Izumi et al. [40] and gives, under optimized conditions, e.e.s >90% in the hydrogenation of -keto esters. Even with simple ketones good results are obtained, e.g., 2-octanone 80% e.e. [41]. As yet the mechanism of the enantioselectivity is not well understood. 

IrCl(cod)]2, in the presence of PPh3 and KOH, catalyzed the a-alkylation of ketones with alcohols [41]. As an example, the reaction of 2-octanone 87 with 1-butanol 88 was catalyzed by the iridium complex to give 6-dodecanone 89 in 80% yield (Equa-hon 10.19). The alkylation proceeded with complete regioselectivity at the less-hindered side of 2-octanone, and the reaction was promoted by a catalytic quantity of KOH (10mol%) in the absence of both a hydrogen acceptor and a solvent. 

CH3(CH2)4CH(0H)CH2CH3, CgHigO, M, 130.23, bp9i.6 A> 176-176.5 °C 0.8264, Up 1.4252, may occur in its optically active form. It is a colorless liquid that has a mushroomy-earthy odor and occurs in mushrooms. 3-Octanol can be obtained by hydrogenation of 3-octanone it is used in lavender compositions and for imparting mushroom-like odors. 

Fig. 16. Relation between the optical yield and the amount of pivalic acid and acetic acid in ihe cnanlioface-difl erentiating hydrogenation of 2-octanonc with TA-NaBr- MRNi (O) pivalic acid (A) acetic acid. Catalyst standard (see Table IX). Reaction conditions 2-octanone (10 ml), THF (20 tnl). acid. 100 C, 90 kg em2.

Effect of Additives on the Optical Yield in the Enantio-Differentiating Hydrogenations of 2-Octanone and MAA with TA-NaBr-MRNi... 

The photochemistry of certain A-substituted heterocycles has also been studied. As part of a continuing investigation of the photolysis of A-nitroso compounds in solution, the conversion of A-nitroso-3-azabicyclo[3.2.2]nonane (65) into the oxime (66) by photolysis in the presence of acid was reported.58 N-Nitrosopyrrolidine is similarly transformed. The mechanism of this reaction is said58 to involve elimination of NOH with the formation of an imine as intermediate, and, in fact, in the photolysis of 2-ethyl-A-nitrosopiperidine (67), the tetrahydropyridine (68) is the major product. This mechanism certainly does not operate in the photolysis of iV-nitroso-2-azacyclo-octanone, which can be rationalized on the basis of an intramolecular hydrogen transfer [Eq. (16)].59 Acyclic iV-nitrosoamides behave in a similar fashion to IV-nitrosoamines.60... 

Irradiation of 2-octanone and 2-nonanone in isooctane gives the expected products plus 2-n-propyl-l-methylcyclobutanol (Formula 256) (R = ra-Pr) and 2-w-butyl- 1-methylcyclobutanol (Formula 256) (R = n-Bu) (102). The formation of the cyclobutanols may be rationalized as the cyclization of a diradieal formed by 7-hydrogen transfer. 

Methyl radicals generated by electrolysis of acetic acid can be used for radical substitution of aldehydic hydrogen or a-hydrogen in ketones. As an example, enanthaldehyde yields 2-octanone, 2-octanone 3-methyl-2-octanone, and benzal-dehyde acetophenone on electrolysis in aqueous acetic acid 197 ... 

Optical yields as high as 56% (but more typically 10-20%) have been recorded by Solodar (41) in the direct asymmetric hydrogenation of ketones with [Rh(COD)(ACMP)2] + BF4. 8 Catalyst turnover ratios of over 1000 were observed. It was found that the stereochemistry was quite dependent on the choice of solvent and its water content. For example, the hydrogenation of 2-octanone in ethanol gave the (+)-S-carbinol with 1.6% ee in N, Af-dimethyl-formamide (DMF) the i -carbinol was observed in 5.1% ee, and in acetic acid the R-carbinol was observed in 12.0% ee. In varying the water content of the isobutyric acid solvent in the hydrogenation of 2-octanone from 0.1 to 8%, the optical yield dropped from 13.9 to 5.3%. 

Bicyclo[3.3.0]octanones are photolabile in their own right and experience ring opening when irradiated. Coyle has demonstrated that the overriding factor in product formation from the diradical intermediates is the distance between the hydrogen atom which is transferred and the radical center to which it migrates.l96)... 

A recent investigation of the intramolecular photoreactions of 2-pentanone, 2-octanone and 5-methyl 2-hexanone in solution indicated that the intramolecular abstraction of a tertiary hydrogen atom from the y-position is faster than that of a secondary one, which in turn is faster than the abstraction of a primary H atom. This was found to be equally valid for the reactions of the triplet and the excited singlet states. 

The reaction actually produces a mixture of the primary amine and the correspond ing formyl derivative, but the amine product is exclusively isolated after the crude product is treated with H Cl (Scheme 7.3). As of this writing, the method provides low yields and ee for cyclic aromatic substrates, for example, 1 indanone (6% yield, no ee reported, chiral Ru catalyst) [11b]. Regarding aliphatic ketones, for example, 2 octanone (44% yield, 24% ee, chiral Ru catalyst [lla[ or 37% yield with an achiral Rh catalyst [11b]). The same authors have recently made inroads concerning the use of aromatic ketones and molecular hydrogen [12], although the transfer hydrogenation method presented here appears to be superior as of now. 

FNiP was Irealcd with a hydrogen slreani al 200 C. Modification pH 3.5 Reaction mixture 3-octanone (32m mol), THF (lOml) and pivalic acid (8.15g) Hydrogenation temperature lOOX... 

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