Other Cyclic Ketones

Other Cyclic Ketones. Structure and photochemical reactivity of the following cyclopropyl and olefinic cyclic ketones were studied by Hess and Pitts (112)  

Compounds I and III at 313 and 238-265 nm photodecompose efficiently to CO and hydrocarbon products (i.e., l co = 0.77 and 0.87, respectively). In contrast, compounds II and IV photode-composed much less efficiently under identical conditions. However, compound II photoisomerized efficiently to 3-methyl-2-cyclopentenone. This rearrangement is comparable to the photoisomerization of methylcyclopropyl ketone to methylpropenyl ketone (190). 

The lower triplet state corresponds to the 3a (3a ) transition of the tt,x type. This band could underlie the 385-to 200-nm band since the Franck-Condon accessible region may be quite high in energy. Excited electronic states of ketene have been recently studied by electron impact spectroscopy (87). 

Photodecomposition. The facts that the absorption spectrum is diffuse and that there has been no emission observed from ketene suggest that the excited singlet state of ketene is extremely short lived. An upper-limit lifetime of t 4 x 10 s has been deduced by Zabransky and Carr (257). The study of ketene photochemistry has had to rely on the measurement of CH2(x3bi) and CH2(al-A ) yields - a notoriously difficult task. 

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The retentive power of graphite towards adipic acid and the catalytic effect of the magnetite, especially present in A, are obvious. TEM examinations of a graphite A sample before and after reaction showed that crystallites of Fe304 appeared to be smaller after the reaction. However, the same graphite sample was reused for three successive reactions without significant loss in yield. When applied to the synthesis of other cyclic ketones (Scheme 7.14), less volatile than 74, it was observed that pressure had an effect on the recovery of product (Tab. 7.9, entries 3 and 4). A slightly reduced pressure (300 mm Hg) was necessary to obtain 3-methylcyclopentanone (75) or cyclohexanone (76) in convenient yield (Tab. 7.9, entries 4 and 5). For the cycliza-tion of suberic acid (73), a less favorable structure, the yield in cycloheptanone (77) remained low (Tab. 7.9, entry 6). 

In a similar fashion some other cyclic ketones can be converted to their imines (see Table 1). 

Cyclohexanone Peroxide. The compn of peroxides obtd from the interaction of cyclohexanone other cyclic ketones with hydrogen peroxides has been a controversial matter. Milas (Ref 3) claimed to have obtd from an ethereal soln of H202 cyclohexanone ... 

Heterocvcl c (see also Other Cyclic Ketones) Ketoaclds and Derivatives Other Cyclic Ketones... 

KETONES (see also HETEROCYCLIC COMPOUNDS and IMIDES))(cont.) Other Cyclic Ketones (cont.1... 

The pyridyl analog (51) leads to the opposite asymmetric orientation in most cases. Asymmetric reduction of 2-cyclohexenone affords (/ )-2-cyclohexenol with 98% ee. Other cyclic ketones are also converted to (f )-carbinols in high optical yields (Scheme 9), but the reduction of acyclic ketones is only moderately stereoselective. ... 

The reactions taking place in the vapour phase also occur in the condensed phase, and their mechanisms are probably similar. However, as may be expected on the basis of the results obtained for the gas phase photolysis, the formation of olefins, cycloparaffins, and CO is of less importance, while that of the saturated aldehydes is more important in the liquid phase or solution, where energy dissipation by collision is more efficient. The decarbonylation products were shown to be only of minor importance in the photolysis of liquid cyclopentanone and cyclohexanone . The unsaturated aldehyde was found to be the main product in the liquid-phase photolysis of cyclopentanone (methyl cyclohexanone . Unsaturated aldehydes were also identified in the photolysis products of other cyclic ketones in the liquid phase as well as in solution . ... 

Similar tendencies are observed with other cyclic ketones. With 2- or 3-methylcyclohexanone, MeLi-LiX (X = CuMe2, CIO4) or MeTi(OPr )3 favors equatorial attack, whereas Me3Al (3 equiv.), MeLi-MAT, or MeLi-MAD attacks from the axial site (Figure 3). ... 

This reaction, similar to the reductions of other cyclic ketones, shows higher selectivity when nonfermenting baker s yeast is used 89,155. Bicyclic /J-keto esters from 1- or 2-tetralone derivatives are also accepted as substrates and are transformed selectively by yeast89,151 153. 

When a 2-alkylbenzo[b]thiophene undergoes Friedel-Crafts acylation with A1C13-cinnamoyl chloride, the resulting 3-ketone cyclizes spontaneously into the 4-position with loss of benzene to give the cyclic ketone 124.515 With 2-bromobenzo[b]thiophene, a similar reaction gives a mixture of 124 [R = Cl (sic)] and the 2-Br, 3-COCH2CHPh2 substituted benzo[f>]thiophene derivative with 2-methoxybenzo[h]thiophene, the ether is demethylated to give 124(R = OH).516 The formation of other cyclic ketones by intramolecular cyclization of carboxylic acids will be considered in Section IV,M. 

Sterically hindered ketones e.g. di-/cr/-butyl ketone and 2,2,6,6-tetramethylcyclohexa-none, are not thiated. However, other cyclic ketones, whilst being thiated also undergo other concomitant transformations thus, cycloalkanones 229 yield the trithiaphosphori-nanes 230 ( = 1 or 2) and enethiols are the products from 2-substituted-cyclohexanones Many polycyclic ketones, e.g. 9-acridones , xanthone and benzanthrone, all are simply thiated". The a,j5-unsaturated ketones (chalcones) (X = O R = Bu or Ph) yield the corresponding thiochalcones 231 (Z = S) together with their dimers 232 when reaction occurs... 

The scope of the Friedlander condensation in the preparation of chiral alkyl-substituted 1,10-phenanthrolines was investigated. A range of chiral [x, y-fc]-cycloalkeno-condensed phenanthrolines 343 and 344 were prepared in one step from the chiral pool of steroidal 342 or other cyclic ketones and 302 via base-catalyzed conditions (Scheme 73) (00MI423, 01JOC400). In the case of the major product, aldol bond formation takes place from the sterically less hindered a-carbon (C2) 343 while the steri-cally more hindered a-carbon (C6) 344 reacts to form the minor product (Scheme 73). 

L-Proline is unable to catalyze the homoaldol reaction of ethyl pyruvate [166]. However, catalyst 155 produces a t/-adducts when cyclohexanone (57) is used as a donor [167]. Disappointingly, other cyclic ketones failed to give desired products in... 

The L-proline-derived phosphinoxide (242) has been reported to catalyse the asymmetric Michael addition of cyclohexanone and other cyclic ketones to chalcones in Pr OH/Bu OH with <99% ee and up to >99 1 dr. NMR and ESI-MS spectroscopy shed some light on the mechanism. ... 

Tetrazoles have been prepared from many other cyclic ketones such as polymethylene cycloketones, " camphor, and thujone. ... 

Carbon nucleophiles enamines Michael addition of cyclohexanone and other cyclic ketones to chalcones Ar CH=CHCOAr, catalysed by the pyrrolidine-based phthalimide and/or 1,8-naphthalimide (316) (30mol%) in the presence of PhC02H (10mol%), neat at 20 C, has been found to exhibit good stereoselectivity (<99 1 dr, <96% ee) Similar results were obtained with the C2-sytnmetric tetraamine (317) as 0 catalyst (20 mol%) with <99 1 dr and 93% ee in the presence of 4-Me0-C6H4C02H (20 mol%) (neat, r.t.). Here, a mechanism has been proposed, based on the ESI-MS study of the intermediates. ... 

The ultraviolet absorption spectrum of cyclohexanone reflects the n jt transition common to all carbonyls see figure IX-E-1. The data derived from gas-phase measurements of the cross sections for cyclohexanone from two different research groups [National Center for Atmospheric Research (NCAR) and Ford Scientific Laboratories (Ford)] are in reasonable agreement (Iwasaki et al., 2008). The cyclohexanone cross sections as measured in cyclohexane solution by Benson and Kistiakowski (1942) had indicated seemingly low values (cross sections shown here is significantly less than those observed for cyclopropanone, cyclobutanone, and cyclopentanone, and in fact, all other carbonyls considered in this work. It is not obvious why these significant differences exist in the probability for the n -> 7T transition for cyclohexanone and that of the other cyclic ketones and most other carbonyl compounds. Theoretical studies will be important in defining the reasons for these differences. 

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