Catalytic reduction of 2-dichloromethyl-1,3-dioxolanes with (iso-Bu) 2AlH

Full text of DOI:10.1134/S001250080910005X

ISSN 0012ꢀ5008, Doklady Chemistry, 2009, Vol. 428, Part 2, pp. 250–251. © Pleiades Publishing, Ltd., 2009.
Original Russian Text © L.N. Ivanova, O.S. Vostrikova, S.S. Zlotskii, 2009, published in Doklady Akademii Nauk, 2009, Vol. 428, No. 6, pp. 765–766.
CHEMISTRY
Catalytic Reduction of 2ꢀDichloromethylꢀ1,3ꢀdioxolanes
with (isoꢀBu) AlH
2
L. N. Ivanova, O. S. Vostrikova, and S. S. Zlotskii
Presented by Academician N.S. Zefirov April 9, 2009
Received April 22, 2009
DOI: 10.1134/S001250080910005X
It was previously shown that cyclic acetals and ketꢀ
Reaction mixture contains no products resulting
als readily undergo reduction and ring opening when from the opening of dioxolane ring (compounds comꢀ
reacted with dialkylaluminum hydrides to form correꢀ prising a hydroxy group).
sponding glycol monoethers [1–3]. It is also known
The catalysts used were alkoxides and complexes of
Ti and Zr: (nꢀBuO) Ti, ZrCl , Cp TiCl , Cp ZrCl
4 4 2 2 2 2
table).
The yield of compound IIa varied in a wide range
from 15 to 99%) depending on experimental condiꢀ
that (isoꢀBu) AlH in the presence of Ti and Zr comꢀ
2
plexes reduces a gemꢀdichloromethylene group to
chloromethylene one [4]. It was interesting to reveal
the direction and results of catalytic reduction of 2ꢀ
(
(
dichloromethylꢀ1,3ꢀdioxolanes (Ia, Ib) with (isoꢀ
tions. Quantitative yield was obtained at 75
°
C when
Bu) AlH (Scheme 1). Compounds Ia, and Ib form in
2
twoꢀ to fourfold excess of (isoꢀBu) AlH was used in the
2
practically quantitative yields when dichlorocarbene
combines with corresponding cyclic acetals [5, 6].
presence of (
nꢀBuO) Ti or Cp ZrCl . Compound IIa
4 2 2
partially decomposes to give phenyl chloromethyl
We have found that (isoꢀBu) AlH in 1,4ꢀdioxane ketone (not more than 5%) when the reaction was carꢀ
2
medium in the presence of catalytic amounts of Ti and ried at 90
Zr complexes converts compounds Ia and Ib into corꢀ
responding 2ꢀchloromethyl derivatives (Ia Ib),
whereas in the absence of the noted catalysts the initial
°
C for 8 h.
The reduction of ketal Ib proceeds much more difꢀ
ficult and the yield of monochloro derivative (IIb
does not exceed 22%. In this case, only Cp TiCl
,
)
2
2
dioxolanes (Ia, Ib) were recovered intact from reaction
shows catalytic activity. No reaction is observed in the
presence of other catalysts (the table).
mixture.
It should be noted that we failed to convert Ib into
(
iso-Bu) AlH, catalyst
2
O
R
O
IIb using such reagents as LiAlH [7] and zinc dust [8].
4
The relative reactivity of compounds Ia and Ib was
CH Cl
2
assessed by competitive reactions with (isoꢀBu) AlH in
2
O
R
O
(
IIa, IIb)
the presence of Cp TiCl . Benzaldehyde acetal Ia
2
2
proved to be four times more reactive than isobutyralꢀ
dehyde derivative Ib, which agree well with above
results (table).
CHCl2
(Ia, Ib)
(
iso-Bu) AlH, catalyst
2
O
OH
Let us note that the products of complete reduction
R
H
of compounds (Ia, Ib) were not found, whereas the
CHCl2
reaction of (isoꢀBu) AlH with gemꢀdichlorocycloproꢀ
2
panes leads to a partial formation of carbocycles conꢀ
taining no chlorine atoms [4].
R = Ph (Ia, IIa)
R = iso-Pr (Ib, IIb)
Scheme 1.
EXPERIMENTAL
Initial 2ꢀdichloromethylꢀ1,3ꢀdioxolanes (Ia, Ib)
were obtained by the known procedure [6], distilled in
an argon flow, and stored in an inert atmosphere. The
reactions were carried out using a commercial solution
Institute of Organic Chemistry, Ufa Research Center, Russian
Academy of Sciences, pr. Oktyabrya 71, Ufa, 450054 Russia
Ufa State Oil Technical University, ul. Kosmonavtov 1, Ufa,
4
50062 Russia
of (isoꢀBu) AlH. All experiments with the use of orgaꢀ
2
250

CATALYTIC REDUCTION OF 2ꢀDICHLOROMETHYLꢀ1,3ꢀDIOXOLANES
251
Effect of catalyst nature, temperature, and reaction time on of NaF was added, and the mixture was stirred vigorꢀ
the yields of 2ꢀchloromethylꢀ1,3ꢀdioxolanes (IIa, IIb)
ously for 0.5 h to form a complex of (isoꢀBu) AlH with
2
NaF. The reaction mixture was quenched by dropwise
addition of 0.5 mL (30 mmol) of water, stirred until gas
evolution ceased, the precipitate was filtered off and
washed on the filter with 1,4ꢀdioxane, the combined
filtrates were concentrated, and the residue was disꢀ
tilled in vacuum.
Yield of reꢀ
С Time, h action prodꢀ
ucts, %
Initial
compound
Catalyst
ZrCl4
Т
,
°
Iа
Ib
Iа
Ib
Iа
Iа
Iа
Iа
Iа
Ib
Ib
Ib
Ib
Ib
Ib
Ib
Iа
75
90
75
90
75
75
75
75
90
75
90
90
90
90
90
90
75
6
8
72
ZrCl4
–
1H NMR (CDCl3,
, ppm): 3.35–3.75 (m, 4H,
δ
Cp ZrCl
2
6
≥
99
2
2
CH ), 3.61 (s, 2H, CH Cl), 7.12–7.57 (m, 5H, Ar).
Cp ZrCl
2
8
–
2
2
2
1
3
C NMR (CDCl3,
δ
, ppm): 49.4 (CH Cl), 65.6
2
Ti(
Ti(
Ti(
Ti(
Ti(
Ti(
Ti(
n
n
n
n
n
n
n
ꢀBuO)4
ꢀBuO)4
ꢀBuO)4
2
15
(
(
2CH ), 107.9 (C arom.), 126.4 (2CH arom.), 128
CH arom.), 128.5 (2CH arom.).
2
4
48
6
≥
99
2ꢀChloromethylꢀ2ꢀisopropylꢀ1,3ꢀdioxolane (IIb).
ꢀBuO)4
2
≥
99*
65*
The cleavage of Ib was carried out as described above.
2ꢀChloromethylꢀ2ꢀisopropylꢀ1,3ꢀdioxolane (IIb) was
ꢀBuO)4
8
isolated by column chromatography with hexane–
ꢀBuO)4
ꢀBuO)4
6
–
1
ethyl acetate (7 : 3) as eluent. H NMR (CDCl ,
δ
,
3
8
–
ppm,
J
, Hz): 1.16 (d, 6H, 2CH , (CH ) CH,
J
= 6.9),
3
3 2
Cp TiCl
2
8
4
2
2
2
2
2
2
2
.25 (m, 1H, CH, (CH ) CH,
J = 6.9), 3.57 (s, 2H,
3
2
Cp TiCl
2
12
16
20
8
11
20
22
13
CH Cl), 4.05–4.15 (m, 4H, 2CH ). C NMR
2
2
Cp TiCl
2
(CDCl3,
δ
, ppm): 16.4 (2CH ), 32.7 (CH), 45.6
3
(
CH Cl), 65.9 (2CH ), 110.5 (C).
Cp TiCl
2
2 2
Cp TiCl
2
4*
20*
Thus, we have established that organoaluminum
compounds reduce the halogen in 2ꢀdichloromethylꢀ
,3ꢀdioxolanes without affecting the cycloacetal fragꢀ
ment.
Cp TiCl
2
6
1
Note: Molar ratio (Ia, Ib) : (isoꢀBu) AlH : catalyst = 5 : 10 : 0.08,
2
the chemicals were dissolved in 10 mL of 1,4ꢀdioxane.
*
Molar ratio (Ia, Ib) : (isoꢀBu) AlH : catalyst = 5 : 20 : 0.08.
2
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1
2
3
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argon atmosphere. The qualitative and quantitative
analysis of initial mixtures and reaction products was
performed on a Chromꢀ5 chromatograph equipped with
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1
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5
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7
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2
ꢀChloromethylꢀ2ꢀphenylꢀ1,3ꢀdioxolane
(IIa).
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2
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strate (Ia) and 0.027 g (0.08 mmol) of (
0 mL of 1,4ꢀdioxane at 0 C with vigorous stirring in
an argon flow, heated to 75 C, and stirred for 6 h at
C. The mixture was diluted with an equal volume
of anhydrous benzene, cooled to 0 C, 1.3 g (30 mmol)
nꢀBuO) Ti in
4
6
1
°
°
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1
7
5
°
°
DOKLADY CHEMISTRY Vol. 428
Part 2
2009