9-Methyl-l-decalone

A similar dissection of the excited states responsible for reaction by quenching has been carried out on cis- and /ra 5-8-methyl-1 -hydrindanone and cis- and frans-9-methyl-l-decalone with the purpose of determining the... 

Methylcyclopropene, 178 l-Methyl-rrans-2-decalone, 179 cis-9-Methyl-l-decalone, 179, 180 frans9Methyl-l -decalone, 179—180 Methyl desisopropyl dehydroabietate, 180-... 

Table 4.4. Cleavage and Isomerization of 8-Methyl-l-hydrindanones and 9-Methyl-l-decalones ...

In a redetermination of the 5a- and 5P-cholestan-4-one equilibrium it was found that 87 + 1% of the 5a-species is present at 25°C in ethanol. For 9-methyl-l-decalone the cis-isomer is favoured at equilibrium, and for 10-methyl-1-decalone the trans-isomer is favoured. These results are supported by molecular mechanics calculations. The amount of cis-isomer contained in equilibrium,mixtures of 1-decalones is larger than in the steroidal counterparts, and this was rationalized in terms of the two low-energy a s-conformers which are available in the cis-decalones. 

Although the n-butylthiomethylene group is subject to acid hydrolysis, basic conditions for hydrolysis have been developed and these seem to be preferred in actual practice. A typical procedure uses a mixture of a 25% aqueous potassium hydroxide solution with ethylene glycol heated at reflux. In this manner thioenol ether 101 was converted to 9-methyl-l-decalone (102) in 78% yield (equation 82). The rare use of acid hydrolysis is exemplified by the use of concentrated hydrochloric acid to hydrolyse the blocked lactone (104) to 105 (equation 83) . Additional examples of conversions using a thioenol ether intermediate are shown in Table 2. 

Dimethylcyclohexanone and 2-benzyl-2-methylcyclohex-anone have been prepared similarly in yields of 60% and 55%, respectively.2 The procedure has been extended to the synthesis of 9-methyl-, 9-w-butyl-, and 9-benzyl-l-decalone from the dianion of 2-formyl-l-decalone in yields of 55%, 48%, and 58%, respectively.2... 

Exo cycloalkylations have been used to synthesize ct5-1-decalones. For example, treatment of 2-methyl-3(4-tosyloxybutyl)cyclohexanone with sodium t-pentylate in benzene gave c/j-9-methyl-l-deca-lone (50) in 60% yield. Also, as shown in Scheme 28, conjugate addition-cycloalkylation was employed to synthesize a cw-fused decalone related to the sesquiterpene, ( )-valerane. Apparently, in these cases, the enolate intermediate adopts a conformation having the 4-bromobutyl side chain quasi-axial, and C—C bond formation occurs via equatorial attack to give initially a twist-boat conformation of the product. 

The THF conditions were also used for alkylation of Awi0)-l-octalone (10). Some alkylation occurred at the 2-position, but the main products (62%) were cis-and frans-9-methyl-1 -decalone, (II) and (12). in the approximate ratio 3 1. 

Methyl-(roni-l-decalone, 381 10-Methyl-rriJ j-3-decalone 601, 602 10-Methyl-dj-2-decalone-9-ol, 700... 

All lations of the protected ketones are very facile. The thioenol ether generally need only be left in contact with the base a few minutes before addition of the alkyl halide. Such short contact with the base allows easy isolation of the alkylated, blocked ketones. Thus, 2-/ -butylthiomethylene-1-decalone (100) was converted to 9-methyl-2-butylthiomethylene-l-decalone (101) in 85% yield. This procedure was used in the difficult dimethylation of 103 to give the lactone 104. 

Reductive alkylation and carbomethoxylation. Stork1 has now published details of his method of generating the less stable enol of an a,/3-unsaturated ketone and trapping this intermediate by alkylation or carboxylation before equilibration can occur (1, 601-602). For example, reduction of A1<9>-2-octalone (1) with lithium-ammonia followed by addition of methyl iodide instead of the usual proton source gives in about 50% yield a mixture of l-methyl-fra/is-2-decalone (2, 83%) and the product of reduction, fron.r-2-decalone (3,17%). Direct alkylation of trans-2-... 

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