9-Fluorenone reduction

The 9-carbonyl group of diazafluorenones behaves in an analogous manner to that in fluorenone reduction to the 9-ol and to the fluorene <70AJC1023>, reaction with dialkyl phosphites to yield 9-hydroxy-9-phosphonic esters <84JPR349>, and with acetone to give the 9-hydroxy-9-(2-oxopropyl) analogue <62CB2137>. 

FIGURE 13.6 Fluorenone reduction reaction mechanism. (Adapted from Nakagawa, K. and Minami, K., Tetrahedron Lett., 5, 343-346, 1972.)... 

The rho values (2.78 overall, 3.78 for reduction to the cis product and 1.96 for reduction to the trans), determined from a study of the rates of reduction with NaBH4 of a series of 4-substituted cyclohexanones, have been interpreted as supporting a transition state late in the reaction.Other groups have observed positive rho values (2.5 to 3.1) for the reduction with NaBH4 of fluorenones and acetophenones. These results show clearly... 

Similarly, the hydride reduction of the fluorenone and anthraquinone complexes gives the corresponding secondary alcohols with endo-OH groups resulting from stereospecific attack [134], This strategy is also known in the Cr(CO)3(arene)... 

TABLE 5. Reduction potentials (volt) of thioxanthone (TOS) and its oxides (TOSO, T0S02) compared with that of fluorenone (FIO)... 

Figure 3 shows the cyclic vo1tammogram of an aceton i tr i 1 e solution containing 9-fluorenone on a bare Pt electrode and on a Polv-1 coated Pt electrode using II as the electrolyte. The only significant difference between the vo1tammograms is the presence of the poly-I reduction and oxidation waves for the coated electrode. We have previously determined by other means that poly-I films should not be permeable to molecules as large as 9-... 

The stereoselective 1,4-addition of lithium diorganocuprates (R2CuLi) to unsaturated carbonyl acceptors is a valuable synthetic tool for creating a new C—C bond.181 As early as in 1972, House and Umen noted that the reactivity of diorganocuprates directly correlates with the reduction potentials of a series of a,/ -unsaturated carbonyl compounds.182 Moreover, the ESR detection of 9-fluorenone anion radical in the reaction with Me2CuLi, coupled with the observation of pinacols as byproducts in equation (40) provides the experimental evidence for an electron-transfer mechanism of the reaction between carbonyl acceptors and organocuprates.183... 

Refluxing of 9-fluorenone-l-carboxylic acid with zinc dust and copper sulfate in aqueous potassium hydroxide for 2.5 hours afforded 9-fluorenol-1-carboxylic acid in 94% yield [1004]. Reduction with sodium borohydride in aqueous methanol at 0-25° converted 5-ketopiperidine-2-carboxylic acid to /ra j-5-hydroxypiperidine-2-carboxylic acid in 54-61% yield [1005], On the other hand, reduction of V-benzyloxycarbonyl-5-ketopiperidine-2-carboxylic acid gave 89% yield of V-benzyloxycarbonyl-cis-5-hydroxypiperidine-2-car-boxylic acid under the same conditions [1005],... 

The above ideas fit in nicely with the work of Cohen and Guttenplan223 who reported the photoreduction of fluorenone by triethylamine. Dilution of neat triethylamine with cyclohexane increased the quantum yield of reduction by decreasing the amount of singlet quenching.221... 

The reactivity pattern for the reduction of fluorenone—sporinite > vitrinite > alginite > semifusinite > fusinite > resinite—defines a bell shaped dependence on the H/C ratio of the maceral and presumably reflects the quantity of readily oxidized hydroaromatic compounds in the maceral. The differences in the effectiveness of the macerals depends in part upon their ability to initiate the reduction of the ketone and in part upon the facility with which they undergo oxidation. 

Ketone Reduction. Pure samples of representative compounds were reacted with fluorenone to define the general pattern of reactivity. In a typical experiment, fluorenone (0.025 mmole), the hydroaromatic compound (0.025 mmole) and benzene (50pl) were reacted in an argon atmosphere in a glass vessel at 400°C for 60 minutes. The composition of the solution at the end of the reaction was determined by gas chromatography. The results for the seven compounds examined in this work are summarized in Table V. 

Table VII. The Reduction of Fluorenone to Fluorene by Maceral Concentrates from PSOC-1103 and PSOC-828 at 400°C for 1 Hour in the Presence of Benzene3...

Ketone Reduction. The reduction of fluorenone to fluorene was adopted for the study of the donor capabilities of the macerals. The mechanism of this reaction, which apparently takes place in several steps, has not been defined and is currently under study in our laboratory. 

Table VIII. The Reduction of Fluorenone by Macerals and Representative Hydrocarbons at 400°C in 60 Minutes...

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