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 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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