April, 19.50
CARBONATION OF GRIGNARDS OF PRIMARY PROPARGYL BROMIDES
[CONTRIBUTIONKO. 736 FROM
THE
DEPARTMENT O F CHEMISTRY, UNIVERSITY
1639
O F PITTSBURGH]
The Propargylic Rearrangement. I. The Carbonation Products of Grignard Reagents from Primary Propargylic Bromides BY JOHN H. WOTIZ Grignard reagents from primary @-acetylenic bromides was carried out by this author,6 and the present research represents an enlargement upon R' and an extension of that work. The apparatus and method developed by Rowlands, Greenlee, halides of the type R - c s ~ - - x , in which and Boord? for the preparation of Grignard I reagents in high ether dilution were used. The R' R and R1 were phenyl, t-butyl, or alkynyl groups. halides used were of the type RCzCCHtBr, where These halides were converted to organometallic R was the normal propyl, butyl, or amyl group. derivatives which were then carbonated. The They were prepared from the corresponding priacids formed exhibited the acetylenic linkage and mary alcohols using the procedure of Lai,* and were identified by oxidation. However, the car- each was repeatedly distilled under vacuum until bonation of diphenyl-(3-methyl-3-ethyl-l-pen-the major part had a constant refractive index. The Grignard reagents were carbonated by CsHj pouring them on an excess of Dry Ice. Three tyny1)-methyl sodium2(C2H5)2C-C=C-C--Na, and types of acids were isolated from the reaction I I product, R-C=C--CHn-COaH (I), R-C=C=CHz (11), CHI C6H5 I the Grignard reagent of phenyl-t-butyl-t-butylCOzH CeHj and R ~ C , H ~ O ~ C (111). O ~ H The yields of the combined fractions ranged from 3 to 73%, depending , acid ethynylbromornethane, (CH,)zC-C=C-(!-Br on various factors. The products and yields I of some representative runs are listed in Table I, C(CHI)~ and some analytical data in Table 11. . A considerable difference in the yield of acids yielded allenic acids of the type R-C=C=C I was observed when n-butylpropargyl chloride COzH (IV) was used to prepare the Grignard reagents. In no case was the formation of a mixture of the Using the optimal experimental conditions found acetylenic and the allenic acid reported. for the corresponding bromide, the chloride yielded The only @-acetylenichalides that were success- only 22% of combined acids and the ratio of acid fully converted into organometallic compounds I to I1 changed from 1 :5 to 1:3. were the tertiary halides prepared by Marvel and co-workers'*2 which had no hydrogen atoms on Experimental the a-carbons. In attempts to prepare organoIdentification of Products.-Acids of the type I and I1 metallic reagents from other /3-acetylenic halides, were characterized by their melting and boiling points and the coupled hydrocarbon was the main product. by converting them into the solid amides (Table I). Thus, Campbell3 was unable to prepare a Grig- Mixed melting points of isomeric amides showed large deNeutral equivalents (Table 11) were deternard reagent from tertiary @-acetylenic halides. pressions. mined by potentiometric titrations against 0.1 N sodium Lai4 studied the reaction of primary propargylic hydroxide using a Beckman, Model H, PH meter. The bromides with magnesium, but the Grignard carbon skeleton was established by hydrogenation to the reagent, RC=CC!H2MgBr, could not be isolated corresponding saturated straight-chain acids, in the case of of type I, and t o a-alkylbutyric acids, in the case of due to the great reactivity of the halide. The acids of type 11. The semi-quantitative hydrogenation reported products were y-diacetylenic hydro- acids was carried out in absolute ethanol using Adams platinum carbons, RC=C-CH~CHZC=CR. The prod- catalyst under pressures slightly above atmospheric. The ucts were obtained even when the reactions theoretical amount of hydrogen (Table 11) was absorbed were carried out slowly and a t high ether dilution. very quickly with acids of type I, but slowly in the case of acids of type 11. The hydrogenated acids were identified The reaction of 1,4-dichloro-2-butyne with mag- by their neutral equivalents, boiling points, and indexes of nesium6gave only traces of a Grignard reagent. refraction. These values were in excellent agreement with The only previous successful preparation of those listed in the literature and with the measured
In a series of papers dealing with the synthesis and properties of hexasubstituted ethane compounds, Marvel and co-workers' have prepared
