Organic Lab Reactions 191

Organic Lab Reactions 191 - 23 with aluminum isopropoxide...

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186 REDUCTION WITH ALUMINUM ALKOXIDES Limitations of the Method With certain types of compounds this method of reduction fails. In general, /3-keto esters (XX) and /3-diketones which are capable of enoliza- tion form the aluminum salt of the enolic form and are not reduced.* However, if there are no enolizable hydrogens (XXI), reduction proceeds smoothly. If a phenolic ketone or a keto acid forms a salt which is R R R—C—CH—COOC 2 H 6 A1(OR) 8 0 xx R O Al(OR) 2 H R R—C—C—COOC 2 H 6 A1( ° R)8 ) R—C C—COOR 0 R OH R xxr insoluble in the reaction* medium, reduction may proceed slowly or not at all. If the salt is moderately soluble, or if the phenolic or acid group is converted to the ether or ester, reduction will occur. 4-Ketotetrahydrochrysene (XXII) does not undergo reduction
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Unformatted text preview: 23 with aluminum isopropoxide in boiling isopropyl alcohol but can be reduced to the carbinol in 76% yield by substituting toluene as the solvent. Although no reduction of J-menthen-4-one-3 (XXIII) occurs in isopropyl alcohol solution, 24 substitution of the higher-boiling isobutyl alcohol results in an 84% yield of stereoisomeric carbinols. CH 3 xxn xxru Sabina ketone (XXIV) 26 and the esters of chelidonic acid (XXV) 5 are reported not to be reduced by aluminum isopropoxide in boiling iso-propyl alcohol solution. Apparently no attempts have been made to "Bachmann and Struve, /. Org. Chem., i, 461 (1939). 24 Malcolm and Read, J. Chem. Soc, 1939, 1037. Short and Read, J. Chem. Soc, 1939, 1415....
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