with i~Bu2AIH [(Illa):Al = 1:2] in ethereal solvents (dioxane, diethylether, tetrahydrofuran, ... Bu2AIH, 0.08 mmole of catalyst, l0 ml of 1,4-dioxane, 75"C, 6 h].
ORGAHIC
CHEMISTRY
EFFICIENT METHOD FOR THE SYNTHESIS OF MONOHALOCYCLOPROPANES BY REDUCTION OF GEMDIHALOCYCLOPROPANES WITH i-Bu2AIH IN THE PRESENCE OF Ti AND 7r COMPLEXES U. M. Dzhemilev, R. L. Gaisin, A. A. Turchln, N. R. Khalikova, I. P. Baikova, and G. A. Tolstikov
UDC 542.944.2+542.941.7:547.512"121:547.256.2
We have investigated the reductive dehalogenation reaction of alkyl and aryl substituted gemdihalocyclopropanes with diisobutyl aluminum hydride in the presence o/catalytic amounts of titanium and zirconium complexes. As a result we propose a general method for the synthesis o/substituted monohalocyclopropanes and cyclopropanes o/ various structures. We have also studied the stereochemistry o/the reduction. The best known methods for the synthesis of monohalocyclopropanes are based upon use of the reaction of [2+ 1]-cycloaddition of monohalocarbenes to olefins [1] or upon partial reduction of gem-dihalocyclopropanes prepared by the method of Makosh [2]. As reductants are used reagents such as n-BusSnH, LiAIH4, Zn/EtOH, Li/NH s, Na/MeOH, (EtO)2P(O)CH2Li, (MeOCH~CH20)~AINaH ~, H~, and also an electrochemical method [3]. These methods are characterized by low selectivity or require difficultly available organometallie reductants. Earlier we showed that, in the presence of catalytic amounts of Ti and Zr compounds, i-Bu~AIH selectively reduces alkyl, cycloalkyl, aryl, and vinyl ~alides under mild conditions to the corresponding hydrocarbons with high yields [4]. In the present work we have studied the reduction catalyzed by Ti and Zr complexes of alkyl and aryl substituted gem-dihalocyclopropanones by i-Bu2AIH. In order to select the optimal conditions we have studied in detail ihe reduction of l,l-diehloro-2-hexyleyelopropane (IIIa). As a result we have found that (IIIa) on reduction with i~Bu2AIH [(Illa):Al = 1:2] in ethereal solvents (dioxane, diethylether, tetrahydrofuran, diamyl ether) at 75~ (3 h) in the presence of the catalyst (n-BuO)4Ti is converted in quantitative yield to a mixture of cis- and trans- l-chloro2TABLE 1. Influence of the Solvent on the Yield and Composition of the Products of the Reduction of (Ilia), [1.0 g (5 mmoles) of (IIIa) 1.4 g (10 mmoles) of i-BueAIH, 0.0136 g (0.04 mmole) of (n-BuO)4Ti, I0 ml of solvent, 6 h]
Comp. os B
reaction " ~roducts T,*C sion of '-" ~"~M (Ilia),
Solvent
So ivent
(IIrb) (IIIC)n'l
6
67
33
63 68 68
37 32
Diethyl ether I 40
t2 33 46
Diamyl ether / 75
47
57
43
amyl ether I 40 4O Dioxane I 40
32
~.-of
--]
~n'v~-
. i
I T,
~
(IIlb)I (IIIC-)
(llla)'~i~[
Dioxane Diamyl ether
95 95
Dioxane
9~
Benzene
re-
~nver- I action ' prosion of] ducts,
53 53
37 47
61 62
39 38
Institute of Chemistry, Bashkir Scientific Center, Ural Branch, Academy of Sciences of the USSR, Ufa. Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1080-1087, May, 1990. Original article submitted May 18, 1989. 0568-5230/90/3905-0967512.50 9
Plenum Publishing Corporation
967
TABLE 2. Influence of the (n-BuO)4Ti Concentration on the Yield and Stereoselectivity of the Formation of (IIIb, c) [1.0 g (5 mmoles) of (IIIa), 1.4 g (10 mmoles) of i-Bu2A1H, 10 ml of 1,4-dioxane, 75~ 6 h] m0unt0f:~ Conver- Composition pf n-BUO)"~Ti, sion of products, % mmole
!(IIla), %
(IIIb) (III.C) (Ind~
Amount of Conver(n-BuO) ~Ti~ sion of % mmole
0 I 72,28:
0,005 0,0t 0,04
2 37 95
68 68 63
of
Ilia), (ilrb)l(Iiic)J(iiId) (
0,075 0,385 0,77
32 32 37
Composition products, %
98 98 98
64 ] 36 6t ] 37 60 32
2 8
TABLE 3. Influence of the Nature of the Catalyst on the Yield and Composition of the Products of the Reduction of (IIIa) [l.0 g (5 mmoles) of (IIIa), 1.4 g (10 mmoles) of iBu2AIH, 0.08 mmole of catalyst, l0 ml of 1,4-dioxane, 75"C, 6 h] I Comp. of the Conver- [products of the sion of
Catalyst
Catalyst
mi~) ~,Ii.~) tmd) TiC4 ZrC4 (.-BuO) ~Ti
98 98 98
64 66 64
36 34 36
-
CptZrClz CpzTiC12 .
J Conversion of Ilia),
CO . of the prod~ of the reduction ~ %
(Inb)](lllc)I(Ill.d)
tO0 IOD
TABLE 4. Parameters of the PMR Spectra of the Cyclopropane Derivatives (6, ppm; J, Hz; CDCIs; TMS) Coln
.
pound
.
.
.
cis -C~H
trans-C~H
C2H, CSH~
(lb-C)
3,25-3,45m
2.8-3,0 m
0,37 m
(lib--c)
,3,13-3,31m
0,67-t,05 m 2,75-2,87 m I 0,35 m
3,03-3,21m
CHs
Ph
1,15-1,55m 0,97t,1=7,0 t,15- t,55 m 0,95t,l=7,0
0,62-1,1 m
0,44'mr t,2-1,55 rn 0,9t, I=7,0 0,62-0,72 m 0,90- i,09 m 0,4 m 2,63-2,80-m t,0- t,75 m 0,87t, J=7,0
(llIb-c) 3,08-3,18 m 2,66-256 m I
.(]vb-c)
CH2
0,7-0,9 m
~Vb-c )
3,09-3,3 m r
