THE: GRIGNARD RBAGEST WITH TIIIOCYANATI~S.
2.369
[CONTRIBUTION FROM THE GHEMXCAL I,ABORATORY OF THE UNIVERSITY OP IbLlNOIS. ]
E ACTION OF TEE GRIGNARD REAGENT ON THIOCYANATES. BY ROGBRADAMS,H.B. BRAMLET, AND F. N. TBNDICK. Received August 16, 1920.
In a previous paper, a review was given of the various reactions between the Grignard reagent and those organic compounds which contain a cyan radical. In addition, it was shown that cyanamides were readily converted into amidinesl by the action of the Grignard reagent. In this communication the action of the Grignard reagent on alkyl thiocyanates is described. Two main reactions have been shown to take place according to the following equations. RSCN RMgBr --f RSR MgBrCN RSGN RMgBr + RSMgBr RCN
+ +
+
J.
+
RSK Excess (3 moles) of Grignard reagent was always used. It has been found that with aliphatic thiocyanates and the Grignard reagent, a mixture of thio-ether and mercaptan is produced. By the usual method of addition, namely, of the thiocyanate to the Grignard reagent, the yield of mercaptan is higher than when the Grignard reagent is added to the thiocyanate. In the same way, the yield of thio-ether is lower in the former and higher in the latter case. If, after the Grignard reagent and thiocyanate are mixed, the solid and the ether solution are worked up separzteiy, as would be expected, the ether solution yields chiefly thio-ether and the solid material yields chiefly mercaptan. If an aromatic Grignard mixture is used with the thiocyanates, the second reaction is the principal one almost to the exclusion of the first. It might be expected that the RCN produced in the second equation would react with the excess of Grignard reagent to give an addition compound that on subsequent decomposition would yield a ketone. RCN 3. RMgBr + RC(NMgBr)R --+ RCOR. Such a reaction was shown t o take place when phenyl magnesium bromide was employed. Upon decomposition of the reaction mixture with hydrochloric acid, a solid, the hydrochloride of benzophenone-imide, separated, insoliible both in the ether and in the hydrochloric acid layers. Moreover, in the ether layer, a certain amount of benzophenone was obtained. With an aliphatic Grignard mixture, the cyanides produced would be converted into unstable imide hydrochlorides which would yield volatile ketones that could not be separated from the large amount of ether used as a solvent. None of these ketones was isolated when aliphatic Grignard reagent was used. THISJOURNAL, 38, 2768 (1916)
"I%eyields of ~ ~ ~ o - eand t ~ xriercaptans ~ e ~ s %I: e small when the ~ r ~ ~ e and ~~ h ~ o~c y a i ~eare a t e of~ low ~o~~~~~~ ~ ~ weight, due to the f a d &hail.the ~ ~ o ale~ volatile ~ c with t ~the ether which i s use rtsfld thers easily lost. owever, as the LlkwiecuIar w c ~ ~of~ tl1e ~ t ~~r~~~~~~ s ~~~~~~t and the thio ate increaw, the yields o i the ~ ~ ~ ~ando - ~ t ~ ~ ~ e ~ become ~ ~ betler. ~ t a The n use ~ of this reaction for the ~ r e p a r ~ ~ i o ~ ~ of cit her ~ ~ ~ or ~ mercaptanrg o ~ C ~eP liar I ~dly be ~ ~~ ~ s~ becatase ~ res die dtlways obtained and the s ~ ~ a oi~ the a 2~ produds ~ o ~ by ~ r ~ ~ is ~necessary. ~ o ~ a ~ ~ ~ ~ n '.l31e action of p ~ ~ n y l - m a g n e s ibronlide u~ on benzoyl cyanide was shld i d . Several reaction5 took place simultaneously vvith the p r o d ~ c t ~ o ~ of txiphen yl-carbinol, triphenylmethane and benzoic add. The formatiou of the ~ r i ~ h e n y ~ - c ~may r b ~ be ~ o easily l explained by the followkg
~
~
~
~
t
~
~
~
~
-4- Cd&MgBr --+ CbHsCOC6
~~~~~~~~~
iphenyl methane is probably formed as follows, ~ ~ ~ ~ s -t-) RMgBr ~ C --+ ~ ~(C6M5)3CMgBr g ~ r
+ ROMgBr
+
(CGfTI6jJCH The formation of this compound in reactions of an analogous nature has been observed by previous investigators. The benzoic acid probably comes from the hydrolysis of benzoyl cyanide. If, instead of 9 males of Grigaard reagent, only one mole is used, tri~ ~ h ~ n ~ ~ ~ a c etriphenyl-methane t o n i ~ ~ ~ e , and benzoic acid are formed. CeHsCOCN @&jMgBr + ( ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ 6-t- C6WbMgBr ~ ~ ~ --+ ( (C&)30CN ~ ~ g ~ MgTcrz r )4-MgO. C ~ Simultaneous with the study of the Grignard reagent on benzoyl cyanide, which it was hoped would yield 1,2-diketones, the action of the Grignjlrd reagent on dimethyl-oxanilide was investigated in order eo obtain ~ ~ ~ as ~follows. ~ o ~ e s
+
c.
~
~
~
+
~ + RMgBr \ > +~
~
~
c
~
~
CHa
CHS
R CL3&
cH8>N
1
';."-->c
R
i
-x-.
+RC'OCOR
acE-13
OMgBr OMgBr
The results showed, however, that no matter how large an excess of ~ ~ i reagent ~ ~ was a used r ~only one of the carbonyl groups reacted; 3
THISJOURNAL, 39,
aor2 (1916)
C
(
THE GRIGNARD REAGENT WITH TIIIOCYANATES.
2371
consequently, on decomposition, the methylphenyl. amides of a-keto acids were produced. /CHa
N-C!-C-N
11 11
+ RMgBr+
eH '6'
0 0
R I CHa>-;--.CeH6
+ K - C-c--N
C--N
