July 5 , 1964
COMMUNICATIONS TO THE EDITOR TABLE
RELATIVEREACTIVITIES O F OLEFINS TOWARD
Olefin A
\
/CHa
/
\
CH3
c=c
CHI
2731
1
P H E N Y L ( BROMOD1CHLOROMETHYL)MERCURY AND TOWARD SODIUM
k A / k , for CaHaHgCClzBr (duplicate)a.bm6
21.5(23.5)
k a / k , for CChCOtNaC-e
24.8
TRICHLOROACETATE
Over-all yields of Over-all yields of dichlorocycloprodichlorocyclopropanes for CaHsHgCChBr panes for C C l C O z N a reactions”” reactionsh
93.6 (94.4)
87.7
CzHs
c~s-~-C~H~CH=CHC~H~ trans-n-C3H,CH=CHCzHr n-CaHIlCH=CHz ClzC=CHCl
7.16(7.34)
7.35
93.0(95.2)
85.7
3 . 5 3 ( 3 . 5 5 ) 3.550
3.52
93.4 (93.2)
80.9
2.05 (2.09)
2.08
92.0 (92.1)
80.1
1.23(1.22)
1.26
92.8 (94,2)
72.7
1.oo
1.00
0.826 (0.831) 0.523 (0.526) 0 . 512c 0.236 (0.236) 0.0146 (0.0158)’
0,800“ 0.523 0.219
82.9 (86.4) 91.2 (93.4) 8 9 . 6 (91 . 5 ) 85.4 (84.7)
49.7 63.6 60.6
a Reaction time 3 hr. a t 80 f 2‘. * Solvent, benzene. Solvent, 1,2-dimethoxyethane. Reaction time 8 hr. a t 80 f 2’. CO rnOlefins in sevenfold excess. 0 Per cent based on C6H5pared with cyclohexene; both in fivefold excess unless otherwise specified. HgCCIzBr. Per cent based on CC13COzNa. i Yields of C6H5HgBrisolated: 9&97’70.
involved free dichlorocarbene as an intermediate and Force Office of Scientific Research Grant No. AFAFOSR-502-64. CsH5HgCCl~Br reacted as shown in 11. The elimination of the “methylene transfer” mech(20) (a) Alfred P. Sloan Foundation Fellow, 1962-1960; (b) N a t i o n a l Institutes of Health Predoctoral Fellow, 1963-1964. anism leaves for discussion mechanisms involving DEPARTMENT OF CHEMISTRY DIETMAR SEYFERTH~~ attack on the olefin by : CC1z or by :CCI2Br in the case MASSACHUSETTS INSTITUTE OF JAMESM. BURL ITCH^^ of our mercury reagent. The reaction of cyclohexene TECHNOLOGY with the CHClzBr-t-BuOK system has been shown to CAMBRIDGE, MASSACHUSETTS RECEIVED APRIL25, 1964 give ( v i a : CCl2Br) 7,7-dichlorobicyclo [4.1.O]heptane and 7-bromo-7-chlorobicyclo [4.1.O]heptane in 6: 1 molar ratio.” In contrast, the reaction of CeHBHgCClzBr Structural Requirements for Second-Row-Element with cyclohexene gave only 7,7-dich~lorobicyclo[4.1.O]Functional Groups to Preserve Asymmetry heptane and phenylmercuric bromide. lo This sugof Carbanions gests that :?ClzBr is not involved in mercurial-olefin Sir: reactions. For these reasons we favor a mechanism for In previous work three functional groups centered the CsH&$X3-olefin reaction which involves a free about second-row elements have been examined with dihalocarbene intermediate. By implication we also regard to their effect on the stereochemical capabilities favor a free dichlorocarbene intermediate in the of carbanions. The benzenesulfonyl group has been sodium trichloroacetate-olefin reaction. I t is to be demonstrated to preserve the asymmetry of attached noted that both of these systems, mercurials18 and socarbanions’ whereas the benzenesulfinyl and diphenyldium trichloroacetate,’g insert CXz into C-H bonds, a phosphinoxy groups have not exhibited this property.2 reaction currently thought to be one characteristic of ke/k, (ratio of rate constants of base-catalyzed Thus, free carbenes. hydrogen isotopic exchange to that of racemization) A kinetic study of the mercurial-olefin reaction is for I was 2 1 0 in a variety of solvents,Ib whereas the in progress. We present the results above at this 0 CHs CHI CH3 time because of the current interest in the mechanism t I 1 I of these reactions and because we wish to point out CsHsS--*C-D CaH5S-*C-D (Ce,He)zP--*C-D that not all reactions of olefins leading t o cyclopropane J I 4 1 4 1 0 C6H13-n 0 C6H13-n 0 C6Hl3-n formation which involve a metal-containing “divalent I I1 I11 carbon carrier” necessarily proceed v i a transition state
IT. Acknowledgment.-We are grateful for support of this work by the Directorate of Chemical Sciences, Air (17) W. E. P a r h a m a n d R . R. Twelves, J. Org. Chem., 99, 730 (1957). (18) D. Seyferth and J. M. Burlitch, J. A m . Chem. Soc.. 86, 2667 (1963). (19) E. K . Fields, i b i d . , 84, 1744 (1962).
(1) ( a ) D. J. C r a m , W . D. Nielsen, a n d B. Rickborn, J . A m . Chem. Soc., 89, 6415 (1960); ( b ) D. J . C r a m , D. A. Scott, a n d W. D. Nielsen, i b i d . , 83, 3696 (19G1); (c) D. J. C r a m a n d A. S. Wingrove, i b i d . , 86, 1100 (1963); (d) E. J. Corey a n d E . T . Kaiser, i b i d . , 83, 490 (19611, (e) E. J . Corey. H . Konig, a n d T . H . Lowry, Telrahedron Lelters, 18, 515 (19621, ( f ) H . L. Goering, D. L. Towns, a n d B. D i t t m a r , J . Org. Chem., 87. 736 (1962). (2) D . J. C r a m , R. D . Partos, S. H. Pine, a n d H . Jager, J . A m . C h m Soc., 84, 1742 (1962).
2732
COMhlUNICATIONS TO THE
EDITOR
Vol. 86
TABLE I RATIOO F RATECONSTAYTS FOR BASE-CATALYZED HYDROGES I S O T O P E EXCHANGE TVITH MEDICM AND FOR RACEWZATIOS O F FIVE-CARBOY XCIDS Base ----
--Substrate-Run no.
Concn
M
Nature
Solvent
Sature
T
Concn M
O C
Time, hr
Rac
Exch , b
,a
70
70
ke/kac
IYh 0 148 L-BUOD~ L-BUOK 0 020 25 0 4 0-2 41 >28 Yh 0 087 t-BuODd t-BuOK 0 060 25 3 5 6 4 72 19 Yde 0 086 t-BuOH t-BuOK 0 089 25 1 9 3 1 69 37 Yd' CHdOK 0 189 25 4 0 5 3 (CH,),SO' 85 34 0 086 ITde HOCHzCHzOK 0 551 100 14 4 3 (CHz0H)z 0 085 17 53 VIh 0 1i4 t-BuODd t-BuOK 0 245 231 61 6 5 73h 17 i 1 IIh 0 252 ~ - B U O D ~ L-BUOK 1 19 116 45 47 62 1 56 1711dQ 0 256 t-BuOK 1 11 146 69 8 t-BuOH 57 I 2 1 65 VIIIh 1 03 ~ - B ~ o D ~L-BUOR 0 28 100 20 16 5 18 2 1 11 9 10 VIIIh 0 95 t-BuODd l-BuOK 0 28 100 20 17 3 20 2 1 18 a Analyzed by isolation and determination of rotation. * All analyses by combustion and falling drop method. Single-point rate constants. 0.97-0.99 atom of deuterium per molecule. 0.95 atom of deuterium per molecule. 2.6 M in methanol. 0.98 atom of deuterium per molecule. Total exchange 4 atoms of deuterium per molecule; 3.27 atoms of deuterium in phenyl as determined by n.m.r. with methylene iodide as internal standard 1 2 3 4 5 6
-
--
Q
value of the ratio for I1 and I11 was not far from unity in the same solvent^.^ \Ye now report values for ke,'ka obtained for base-catalyzed hydrogen isotope exchange of compounds TV-VI11 with solvents containing the appropriate protium or deuterium reservoirs. Compounds VIIh and VIId were prepared by a refinement of a published procedure,: [a]::: +12.04' for 0
t
CHB 0
CH3
CH30-S-*C-H
'
1
C6H6X--S-
J . 1
0
Iv
0
CsHls-n
CH3
t C~H~--P-*C--H +I I
KO- CsHia-~ VI
0
x-
0 CHI
t*l KO-S-C-H(D) $ 1 +-
0 CfiHi3-n YII
CHB
t *I C-H( 4 1
D)
C6His-n
Table I records the results of the exchange and racemization experiments. The carbon acids whose conjugate bases are stabilized by second-row-element functional groups fall into two distinct classes : those whose exchange reactions exhibit values of ke k , which are well in excess of unity, and those whose values are close to unity. The former systems appear to produce intrinsically asymmetric carbanions which undergo substitution with high retention of configuration. The latter appear to give symmetrical carbanions, and the low stereospecificity exhibited b y the substitution reaction is due to asymmetric solvation effects.
0 CH3
t *I
(c~H~o)~P-c-H
Functional groups which induce carbanion asymmetry
Ct"3-n
VI11
VIIh and [ a ] g i f -12.13' for VIId ( c 5%, water). Conversion of (+)-VIIh to its corresponding acid and treatment with diazomethane gave IV, [a:Iz5obsd. +2.81', X 5460 A,, neat, I = 0.5 dm. The corresponding acids derived from ( - ) - i r I I h and (-)-VIId were converted to their corresponding acid chlorides, which when treated with N-methylaniline in pyridine gave amide products Vh, [a]::, - 1S.27', and Vd -1S.31' (c ;S%, absolute ethanol). No loss in deuterium was noted in passing from the acid chloride to the amide, and thus a sulfene must not be an intermediate.6 Optically active ester VI11 was prepared from optically pure (-)-2-octyl tosylate by a recorded procedure' to give material, [ C Y ] & +6.S3' (c 23%, chloroform). The phosphinic acid derived from salt VI was prepared from optically pure (-)-2--octyl tosylate via its n-butyl ester by refinements of recorded procedures,* +20.15" (c 3%, chloroform). ( 3 ) I). J Cram a n d S. H. Pine, J . A m . Chem. S o c . , 86, 1096 (1963); (b) 1) J . Cram and I
