Reduction of cycloalkanones

Aramendia, MA Borau, V Jimenez, C Marinas, JM Ruiz, JR Urbano, FJ. Meerwein-Ponndorf-Verley reduction of cycloalkanones over magnesium-aluminum oxide. Journal of the Chemical Society Perkin Transactions, 2002 2, 1122-1125. 

MgAl-LDO is also an acUve catalyst for the Meerwein-Ponndorf-Verley reduction of cycloalkanones and substituted cyclohexanones, with the conversion ovct... 

Two new borane reducing agents 135 and 136 have been applied to the reduction of cycloalkanones, a—haloketones, a-amino ketones and aryl alkyl ketones. The effect of... 

A number of papers have appeared dealing with the stereoselectivity of reduction of cycloalkanones with complex metal hydrides. Arguments for - > and against the possible operation of product development control have been offered other investigators remain uncertain. 

Reduction, carboxyl groups, 56,83 Reduction of a,0-unsaturated p-toluene-sulfonyl-hydrazones to alkenes, 59,42 Reductive alkylation, 56,52 Reductive cleavage, 56, 101 Resolution of amines, 55,80, 83 Rexyn 201,55,4 Rhodium(III) oxide, 57, 1 Ring contraction, 56, 107 Ring expansion of cycloalkanones to cycloalkenones, 59, 113... 

Barton put forward the following ideas on the reduction of alkyl cycloalkanones on the basis of conformation. 

Pyridinophanes (96) can be constructed from bis-(/3-chlorovinyl ketonic) intermediates upon treatment with ammonia. Wolff-Kishner reduction of (96) gives the parent (3,5)pyridinophane (68HCA2027). Some /3-aminovinyl carbonyls have been condensed with cycloalkanones in the presence of triethylamine and piperidinium acetate to give the (2,3)pyridinophane series (97) (70TL3291). 

Reduction of N-benzylimines.2 Borch reduction of imines (4, 450) to amines is not stereoselective, although reduction to equatorial amines is somewhat favored. Reductions with 1 and a number of dialkylcyanqborohydrides are much more stereoselective. Thus substituted cycloalkanone imines are reduced mainly to axial amines. However, highest selectivities are obtained with lithium tri-sec-butylborohy-dride (4, 312). 

The stereochemical outcomes of the reductions of cyclic imino derivatives often display surprisingly great differences from those obtained with cycloalkanones and, in fact, attenuations or even reversals in stereoselectivity are common. ... 

Allenyl-substituted cycloalkanones have also been studied the one-electron reduction of these resulted in 5-exo-trig or 5-endo-trig cyclizations (depending on the relative position of the allene group) [95]. The reductive cyclization of ketones in the presence of acrylate side-chains have been investigated the reductant was magnesium metal in methanol [96]. 

The reduction of iV-diphenylphosphinyl imines of substituted cycloalkanones with lithium tri-sw-butylborohydride (L-Selectride) provides highly diastereoselective conversions to protected axial primary amines in 83-96% yield17. The reduction of cyclohexylidene diphenylphos-phinyl imines with sodium borohydride is less diastereoselective17. 

The configuration of the asymmetric carbon in the a-position, with respect to the carbonyl group, is S whereas in the corresponding cycloalkanones it is R (see Section 2.5.1.3.2.1.). In this context it is interesting to note that the reduction of ot,/J-unsaturated ethyl ketones with B. sulfurescens also produces saturated ketones with R configuration49. 

Intramolecular reductive coupling of cycloalkanones tethered to alkynoates in the presence of ( -propene)titanium gives hydroxy esters in a diastereoselective manner (Scheme 191). ... 

Whereas there are many reports on the reduction of steroids [38-43] (although some of these reductions are attributable to the action of bacteria having contaminated the yeast [44]), only a few examples for the reduction of unfunctionalized cycloalkanones [45] have been described [46-48]. 

Notable examples of general synthetic procedures in Volume 47 include the synthesis of aromatic aldehydes (from dichloro-methyl methyl ether), aliphatic aldehydes (from alkyl halides and trimethylamine oxide and by oxidation of alcohols using dimethyl sulfoxide, dicyclohexylcarbodiimide, and pyridinum trifluoro-acetate the latter method is particularly useful since the conditions are so mild), carbethoxycycloalkanones (from sodium hydride, diethyl carbonate, and the cycloalkanone), m-dialkylbenzenes (from the />-isomer by isomerization with hydrogen fluoride and boron trifluoride), and the deamination of amines (by conversion to the nitrosoamide and thermolysis to the ester). Other general methods are represented by the synthesis of 1 J-difluoroolefins (from sodium chlorodifluoroacetate, triphenyl phosphine, and an aldehyde or ketone), the nitration of aromatic rings (with ni-tronium tetrafluoroborate), the reductive methylation of aromatic nitro compounds (with formaldehyde and hydrogen), the synthesis of dialkyl ketones (from carboxylic acids and iron powder), and the preparation of 1-substituted cyclopropanols (from the condensation of a 1,3-dichloro-2-propanol derivative and ethyl-... 

In a similar fashion, reductive alkylation of benzene, toluene, and xylenes with ben-zaldehyde, aromatic methyl ketones, and cycloalkanones can be induced by InCl3 in the presence of Me2SiClH 429... 

Cycloalkenyllithiums.3 Alkenyllithiums are usually prepared by reductive lithiation of trisylhydrazones of ketones with butyllithium, but this method fails with the hydrazones of cyclic ketones. However, the cycloalkenyl sulfides, prepared by reaction of cyclic ketones with thiophenol, can be reductively lithiated with LDBB at -78°. This lithiation fails in the case of cyclopentenyl sulfides, but is useful in the case of the vinyl sulfides obtained from 6-, 7-, and 8-membered cycloalkanones. 

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