I- Decalone

If the enone is part of a decalone system, i.e., a / - and an y-substituent are present, on reaction with lithiated areneacetonitriles in THF the exclusive formation of (Tv-substituted decalones is observedl26. The diastereoselectivity at the exocyclic stereogenic center is, however, poor. Applications in the synthesis of anthracyclines are given in the literature127,12S. 

The isomerization observed in the methylenation of c/s-a-decalones has been turned to good advantage. Mixtures of cis- and tra/is-isomers of the a-decalones (44) and (46) gave only the /ra/i -decalins (45) and (47). 

The ring carbons of the /rans -4-oxodccal i n, (e) of Table 4, lie in the same back octants as those of trans-1 -decalone (a) These perturbers should thus sum to a negative CD. The... 

Table I. (Also continued on next page) Decalones and their conformational representations, Octant Projection Diagrams, predicted and observed n - x CD Cotton effects.

Rings A and B have the same octant perturbers as the corresponding decalone (Table I, entry (b)), but (-) front octant contribution rings C and D, together with (-) back octant... 

In aprotic solvents, an increase in solvent polarity resulted in an increase in the amount of ds-0-decalone formed. Similar results were also obtained in the hydrogenation of cholestenone and testosterone (see Table I). If, as suggested by McQuillin et al. (3), a more polar aprotic solvent will facilitate complexation of the carbonyl oxygen of an a,j3-unsaturated ketonic system in the same way that it increases its polarization (25), it can be assumed that what is occurring in these polar solvents is a 1,4-addition of hydrogen to the conjugated system. 

The morpholine enamine of fra/i.s-2-decalone exists as a 1 4 mixture of A1- and A2-isomers DAD reacts with the former by equatorial attack and the latter by axial attack351 (Scheme 177). In contrast, less electrophilic alkenes, such as / -nitrostyrene and phenyl vinyl ketone, react only with the A2-isomer at C-3 by axial attack (see Section III.B), unless sterically impeded. 

MeAylenation. The reagent reacts with carbonyl compounds to form adducts that are converted into 1-alkenes in 65-95% yield on treatment with silica gel (equation I). Methylenation of c/.r-l-decalone can be effected in 91% yield without any epimerization... 

Benzyl-l-decalone, 48, 43 2-Benzyl-2-methylcyclohexanone, 48,43 N-Benzyloxycarbonylglydne, 46, 49 2-Benzylperfluoropropene, 48,119 C i-2-BENZYL-3-PHENYLAZIRIDINE, 48,20 Benzyltrimethylammonium hydroxide as catalyst for condensation of benzil with dibenzyl ketone, 46, 45... 

The stereochemistry of alkylations of extended dienolates of enones such as (70) has been extensively investigated (Scheme 33).In general, the results are similar to those found for the related decalone enolates (43a) and (44), i.e. steric factors within the anion play a dominant role. Thus, axial attack is preferred with (70 R = H), but equatorial attack is strongly favored when an angular methyl group is present (70 R = Me). There is a modest preference for axial alkylation when an angular ethoxycarbonyl... 

Stork deduced that the octalone (1) should be convertible into the less stable of iwo possible enolates by reaction with lithium in liquid ammonia, and experimentation showed this prediction to be correct. Reduction of the unsaturated ketone (1) afforded only the fru/ij-jS-decalone (3) as the initial product. The reaction is considered to involve addition of an electron from lithium to ketone (1) to produce a hybrid intermediate (2) with carbanion character at the j3-carbon, and this intermediate abstracts a proton from ammonia to form the product (3). These observations suggested a new method of alkylation." Alkylation of the t .v-2-decalone (4) in the presence of base proceeds through the mure stable enolaie and gives (.5). However, the leas stable enulate (2) can be generated by l.i-NH,i reduction of the unseturated ketone (I) and alkylated to give the liomarlu methylated product (A). 

The method has now been used to synthesize 9,10-dimethyl-trarcs-l-decalones,11 which have the characteristic C/D ring system of pentacyclic triterpenes. Thus i ruction of the hydroxy enol ether (9) with the Simmons-Smith reagent gives the cyclopropyl ether (10). Cleavage with 7% methanolic hydrochloric acid leads to the hydroxy ketone (11), convertible by Wolff-Kishner reduction followed by oxidation into (12). 

A nice example of the foregoing stratagem is seen in equation (17) enone (6) undergoes copper(I)-catalyzed reaction with vinylmagnesium bromide from its less-hindered face to give an enolate that reacts with formaldehyde from the opposite face to provide decalone (7), an intermediate in the synthesis of insect antifeedants. Yoshida and coworkers have used this method for the stereospecific generation of tetrasubstituted thioamide enolates, which undergo remarkably stereoselective aldol reactions (equation 18). ° The stereochemistry of this process is discussed in Section 1.6.3.6. 

Gas-chromatographic analysis involved diglycerol (15%, 2 meters, 50°C.) as stationary phase. From trans-Decalin, peaks were trans-9-hydroxy-decalin (t = 41), trans-a-decalone (t = 53), and trans-p-decalone (r = 74) from cw-Decalin they were ci5-a-decalone (t = 30), cis-/3-deca-lone (T = 55) and cw-9-hydroxydecalin (t = 100). Retention times are relative products were identified by comparison with authentic specimens, except for cw-a-decalone, where structure was assumed from retention time and analogy with the trans-series. Peak areas were obtained planimetrically. Relative product concentrations are given in Table I. 

Primary amines RNH2 (R = i-Pr, /-Bu, t-Bu or cyclohexyl) react with the carbamate Et02CN=CCl2 to yield the carbodiimides Et02CN=C=NR. A new method of preparing imines is to add a carbonyl compound (2,6-dimethylcyclohexanone, 2-tetralone, 2-decalone etc.) to a preformed complex of a primary amine (t-butylamine, cyclohexylamine, benzylamine or 1-phenylethylamine) and titanimn(IV) chloride suspended in hexane or octane. Primary amines R NH2 (R = t-Bu, N=C, Tos or phthalimido) react with nitroso compounds R NO (R = r-Bu, pyrrolidin-l-yl, Ph or 2-MeCC6H4) in the presence of the hypervalent iodine compound Phi (OAc)2 to give... 

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