[CONTRIRTTIOV FROM THE D E P A R T M E N T O F CHEUISTRY, [JSIVERSITY O F IIISAOI RI]
The Reaction of 2-(p-Cyanoethyl)-Z-Ethylhexanal with Grignard Reagents NOItLlAN IIABJOHN, 31. J. LATINA,'
AND
L. V. PHILLIPS
Received ivovewkber 9, 1.4.5,5
It has been shown that 2-(~-cyanoethyl)-2-ethylhexanalreacts with aliphatic Grignard reagents to give mixtures which contain 2,6-dialkyl-3-ethyl-3-hutyl-3,1-dihydro-l ,2-pyrans and hydrouynitriles. The dihydropyrans whirh were pwpared were reduced to the corresponding tetrahydropyrans and one of these was converted in lo^ yield to
:t
trtrxalkylmc.th2tne.
The availahility of 2-(P-~yanoethyI)-%-ethylhexanal suggested the possible use of this compound for the synthesis of hydroxy ketones according to the following equation. C4H4-
r I
-CH2CH&N
+ 2 RMgX
1
.O
Followed by hydrolysis
CHO
CdHg-
Y
I H-C-R I
-CH&H,CR
d!
::DOC& CH3
OH
CH3
I11
It was hoped that the latter type compounds, or cyclic analogs which might result from them, could be converted then to certain desired unsymmetrical tetraalkylmethanes. When 2 - ( p - cyanoethyl) - 2 - ethylhexanal was caused to react with 3 molar quantities of several different aliphatic Grignard reagents, it was found that fairly complex mixtures resulted. The separation of these mixtures by distillation n-as complicated by decomposition, but it was possible to obtain in each case a constant low-boiling fraction as well as a less pure higher-boiling fraction. Analytical data and chemical examination of the low-boiling fractions showed that they possessed none of the properties expected of hydroxy ketones. Infrared spectra2 indicated the presence of only very small amounts of carbonyl and hydroxyl functions. It was found that they gave tests for unsaturation, and were hydrogenated over a Raney nickel catalyst. Apparently, the hydroxy ketones which were formed initially suffered enolization and dehydration to give substituted dihydropyrans. In Table I are listed the dihydropyrans which mere prepared as well as the related tetrahydropyrans which were obtained from them by reduction. The dihydropyran structure was substantiated by the ozonization of 2,6-dimethyl-3-ethyl-3butyl - 3,4 - clihydro - 1,2 - pyran (I). Oxidative cleavage of the ozonide afforded acetic acid and (1) Abstracted in part from the Ph. D. thesis of M. J. Latina, 1953.Lubrizol Corporation Fellow, 1951-1952. ( 2 ) The authors are indebted to Dr. E. E. Pirkett for the infrared dnta.
the lactone IT, after hydrolysis of the reaction mixture. Also, treatment of the dihydropyran (I) with ethanol, according to the procedure of Parham and A n d e r ~ o n ,gaye ~ the ethyl 2-tetrahydropyranyl ether (111). The tetrahydropyran (IV) mas
Jv HBr CHaCOzH
H 1- " H CII3-C-C-CHzCHz-C-CHs Rr I Rr CdH, . . / V
J
(1)
(2)
Zn. CHzCOzH H?,Ni
C2Hs
I
C4Hg-C-C4Hg
I
C~HS VI
cleaved by means of hydrogen bromide in acetic acid to a crude dibromide 1' which mas reduced first with zinc and acetic acid and then with hydrogen and Ranev nickel catalyst to produce the hydrocarbon VI. The over-all conversion from the tetrahydropyran to the hydrocarbon was quite lo^ so that the process does not appear to possess much merit. The higher-boiling fraction from the condensation (3) Parham and Anderson, J. Am. Chem. Soc., 70, 4187 (1948).
285
286
RABJOHii, LATINA, AND PHILLIPS
VOL.
21
T.4RLE I DIHYDROPYRANS, C*H!,
R
b p., "C
mm.
CH3 CzHs C6Hl?(n-) C7Hid n-)
85-88' 98-100' 135-138" 133- 135"
1 1 1
'z
Formula
1 4592 1 4602 1 4601 1 4600
CI&~O CiJLs0 CiiHiiO CzdLs0
n
0 05
Inalvses Carbon Hvdrogen Calc'd Found Calc'd Found 79 80 82 82
53 29 07 34
79 38 80 59 81 68 82 16
12 32 12 58 13 18 13 2T
12 12 13 13
42 13 18 01
13.21 l?J .36 13.69 13.75
13.25 13.39 13.78 13.59
c*HQI
