Organic Lab Reactions 197

Organic Lab Reactions 197 - this formation of a lactone...

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102 REDUCTION WITH ALUMINUM ALKOXIDES COOCH 8 r^^f-cooc: !H(CH 3 ) 2 XL VI xx.vn 7-Keto esters,'upon reduction, usually give rise to laotones of the hydroxy acids. The methyl ester of /8-(2-naphthoyl)-propionic acid (XLVIII) was converted in almost quantitative yield a into the corre- sponding butyrolactone (XLIX), A similar reaction was found to occur when the carbon atoms between the ketone and ester groups were included as part of a ring. Methyl l-ketotetrahydrophenanthrene-2- acetate (L) gave an 80% yield of the lactone (LI). 87 With the cis isomer of the cyclopropane derivative (XLIV) lactone formation occurred to the extent of 52%, only a minor portion of .the reduced material being obtained as the isopropyl ester. 40 With the irans.isomer (XLIV), lactone formation is prevented by steric factors. It should be pointed out that
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Unformatted text preview: this formation of a lactone occurs in the reduction mixture in the pres-ence of excess isopropyl alcohol, and not during the subsequent isolation and purification.-CH 2 CH 2 COOCH 3 YT.TY Reduction of Esters of Hydroxy Ketones Because of the catalytic effect of aluminum alkoxides on alcohol exchange in esters, reduction of esters of hydroxy ketones usually i accompanied by cleavage of the ester group and the product is a glycol. Ether and acetal linkages are not affected. Thus, the reduction of the acetate (LII) gave a 94% yield of the glycol (LIII). 42 a Schopf, Brass, Jaoobi, Jorde, Moonik, Neuroth, and Salaer, Ann., 644, 42 (1940)....
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