A STUDY OF REACTIONS OF GRIGNARD REAGENTS AT LOW TEMPERATURES¹

Abstract

The effect of temperature on the course and extent of reactions involving Grignard reagents has rarely been studied below -30°. The outstanding example of a successful result at extremely low temperatures is the formation of acids by treatment of Grignard reagents with solid carbon dioxide (1). Recently it has been shown that at about -70°acetic anhydride reacts with various Grignard reagents to form the corresponding methyl ketones in high yield (2).In this paper we report on further studies of this reaction technique and demonstrate the reason for its success.Effect of temperature. We have studied the reaction which takes place when a solution of butylmagnesium bromide is added to a solution of acetic anhydride in ether at different temperatures. It was found that from the reflux temperature of ether to about -40°the yield of ketone remained almost constant at 50%.2 However, the yield increased rather sharply on further cooling and reached 79% near -70°. One experiment indicated that by going to lower temperatures higher yields might be obtained. However, because of the inconvenience we did not explore this region further. This temperature effect seemed to be about the same in the reaction of i-butylmagnesium chloride with acetic anhydride and of phenylmagnesium bromide with benzoic anhydride. At -70°each gave ketone in about 80% yield but at 0°the yields were about 50%. We did not investigate these cases further but assumed that they were approximately the same as for the case of n-butylmagnesium bromide and acetic anhydride. Our results are summarized in Table I.

Organotin Compounds: Cyclopentadienyl and Related Derivatives

“…A solution with this boiling point is obtained when cyclopentadienylmagnesium bromide is prepared according to the procedure of Courtot. 16 The filtrate was concentrated to 100 ml., and then cooled in a bath of dry ice-acetone. The product was removed by filtration, and dried in a vacuum desiccator to obtain 18.0 g. (59%) of crude phenyltri-l-cyclopentadienyltin melting over the range 43-60°.…”

New sweetening agents. N'-formyl- and N'-acetylkynurenine

“…o-Chloroaniline (Eastman) was converted to a Grignard reagent at 85° ( Spencer and Stokes, 1908). The reaction flask was then cooled in crushed solid carbon dioxide while 5% maleic anhydride in tetrahydrofuran was added drop wise, as described by Newman and Smith (1948). The intermediate product (4) was not isolated but put into a Paar bomb, which was Western Regional Research Laboratory, Agricultural Research Service, U. S. Department of Agriculture, Berkeley, California 94710.…”

NITRO MUSKS. III.1 ASYMMETRICAL MUSKS OF THE DINITRO-tert-BUTYL-m-XYLENE SERIES

“…21.5°and m.p. XXIII with acetic anhydride at low temperature by an adaptation of the method of Newman and Smith (11) led only to the butylxylene (XIII), rather than to the expected asymmetrical acetyl-terf-butyl-m-xylene.…”