Ketones norbomanone

Facial selectivities in the nucleophilic addition of bicyclic ketones have recently been examined comprehensively [71, 72]. Mehta and his colleagues studied the facial selectivities of 2,3-exo,exo-disubstituted 7-norbomanones 14a and 14b [73-75]. In the reduction of 14a and 14b with sodium borohydride, lithium aluminum hydride. 

Cells of Acinetobacter sp. NCIB 9871 grown with cyclohexanol carried out enantiomeri-cally specific degradation of a racemic substituted norbomanone to a single ketone having >95% enantiomeric excess (Levitt et al. 1990). 

Cyclohexanone oxygenase from Acinetobacteria converts a variety of alicyclic ketones into lactones in a regio- and enantioselective manner (Table 12). The reaction can be carried out by a whole-cell process (181) or with the isolated enzyme (178). For example, 2-norbomanone [497-38-1] (112) is converted to the corresponding lactone in 81% yield (178). The enzyme, however, is not selective both enantiomers react equally well. The oxidation rate of camphor [76-22-2] (113), is about one-third that of (112) nevertheless, given sufficient amount of time, the product yield reaches 89%. Substituted cylohexanones (114) and cyclopentanones (115) are converted into the corresponding lactones in moderate to good yield and selectivity (179—181). 

What can be said about the thermochemistry of methylated cyclic ketones in any phase other than liquid In that we would have discussed gas-phase species if the data were available, what we are really asking is what can be said about the species of interest as solids , Let us generalize this to see what can be said about the thermochemistry of cyclic ketones as solids. In that the cyclic ketones in the previous section were all formally quite strain-free derivatives of cyclopentanone or cyclohexanone, let us now consider only such species and their cycloalkane analogs. There are no enthalpy-of-fusion data available for cyclopentanone. For cyclohexanone, the temperature-uncorrected fusion enthalpy is about 1.3 kJmol-1—we arbitrarily ignore in this discussion enthalpies of any crystal - different crystal phase enthalpy. The same treatment for cyclohexane discloses the fusion enthalpy of 2.7 kJmol-1. Accordingly, the earlier reported value of 638(6) = 104.4 for the gas phase is sequentially modified to ca 115 kJ mol-1 for the liquid and to 113 kJmol-1 for the solid. For 2-norbomanone, adamantanone and diamantanone (39a, 42 and 43), the gas-phase differences of 115.7 6.8, 96.0 5.1 and 90.6 3.2 become for the solids 124.4 6.8, 116.9 4.5 and 97.8 3.1 kJmol-1. Very roughly, 639( ) is some 10 kJmol-1 more positive for solids than for gases and 639(8) is about 113 kJmol-1 for all of the solids discussed here. 

Unhindered ketones can be deoxygenated by hydrogenation with this catalyst.4 Stcric hindrance can prevent this reaction. Thus, 2-norbomanone does not react, although camphor is reduced. The alcohols corresponding to inactive ketones are reduced. Cyclopentanone is reduced to cyclopentane in 24% yield cyclohexanone is reduced in 90%yield. When successful, this method is a useful one-step deoxygenation. 

Other cyclic or bicyclic ketones do not have a convex side but only a less concave and a more concave side. Thus, a hydride donor can add to such a carbonyl group only from a concave side. Because of the steric hindrance, this normally results in a decrease in the reactivity. However, the addition of this hydride donor is still less disfavored when it takes place from the less concave (i.e., the less hindered) side. As shown in Figure 10.10 (top) by means of the comparison of two reductions of norbomanone, this effect is more noticeable for a bulky hydride donor such as L-Selectride than for a small hydride donor such as NaBH4. As can be seen from Figure 10.10 (bottom), the additions of all hydride donors to the norbomanone derivative B (camphor) take place with the opposite diastereoselectivity. As indicated for each substrate, the common selectivity-determining factor remains the principle that the reaction with hydride takes place preferentially from the less hindered side of the molecule. 

Norbomanone is a useful starting material for various bicyclic derivatives of theoretical interest. The present procedure provides a convenient method for its preparation and illustrates a general method for the oxidation of formate esters to ketones. 

Nucleophilic addition reactions occur by electron donation from the nucleophile to the IT antibonding orbital of the ketone. If the faces of the ketone are different, addition happens faster at the more accessible orbital lobe. Use SpartanView to display mesh electron-density surfaces of 2-norbomanone and camphor, and simultaneously display the tt antibonding orbital (LUMO) surface of each. Which face of each ketone is more reactive What is the stereochemistry of the alcohol produced by reaction of each with NaBH4 ... 

Vandewalle et al. have also used oxidative ring opening of one side of a norbomanone to prepare a number of iridoids, culminating in a synthesis and correction of the structure of specionin. At first they described the synthesis of teucrium lactone (425) and a loganin precursor (472) from the Diels-Alder adduct 473 of cyclopentadiene and methyl ( )-crotonate (Scheme 44). The same paper describes the preparation of the all-enafo-isomer 474 of ketone 475, from... 

Yates and coworkers " have investigated the reactions of syn- and a /z-7-substituted 3-diazo-2-norbomanones in acidic medium. The products obtained in D2O/D2SO4 mixtures have indicated that these a-diazo ketones can be converted into exo- and endo-diazonium ions by a proton transfer reaction. The ratio of proton transfer to the exo- and endo-fsicc of the diazo ketone was determined from the deuterated l-carboxy-cyclohex-2-enes formed when these a-diazo ketones were reacted in D2O/D2SO4 mixtures (equation 32). 

Lithium acetylide reacts very smoothly with ketones. For example, it combines rapidly with 2-norbomanone (bicyclo[2.2.1]heptan-2-one) to give 1-exo-ethynyl-2-e (io-norbomanol. If camphor is the substrate the ethinyl groups enters on the endo face. The addition of acetylene onto ketones can even be brought about by catalytic amounts of potassium ter/-butoxide. ... 

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