Russian Journal of General Chemistry, Vol. 71, No. 6, 2001, pp. 987 988. Translated from Zhurnal Obshchei Khimii, Vol. 71, No. 6, 2001, p. 1049.
Original Russian Text Copyright 2001 by Kuznetsov.
LETTERS
TO THE EDITOR
Reaction of 2-Isobutyl-4,5-dimethyl-1,3,2-dioxaborinane
with Anhydrous Aluminum Bromide
V. V. Kuznetsov
Ufa State Petroleum Technical University, Ufa, Bashkortostan, Russia
Bogatskii Physicochemical Institute, National Academy of Sciences of Ukraine, Odessa, Ukraine
Received September 15, 2000
As shown earlier [1], the reaction of 2-alkyl- and
2-alkoxy-4-methyl-1,3,2-dioxaborinane withanhydrous
aluminum bromide in benzene involves heteroring cle-
avage to give 1,3-dibromobutane and tert-butylbenzene.
The formation of the latter shows that 1,3,2-dioxa-
borinanes, like acyclic boric esters [2], can be used as
alkylating agents in the Friedel Krafts reaction. The aim
of the present work was to evaluate the reactivity of
stereoisomers of 2-isobutyl-4,5-dimethyl-1,3,2-dioxa-
borinane (I) toward anhydrous AlBr3 in benzene.
According to GLC data, the reaction yields tert-butyl-
benzene (II) and 2-methyl-1,3-dibromobutane (III).
O
B
Br
AlBr3
Me
Me
Bu-i + C6H6
Bu-t + H3C
O
Br
H3C
I
II
III
The formation of compounds II and III was proved
by GLC with use of reference compounds obtained by
independent synthesis [2, 3]. The conversion of cyclic
ester I was no higher than 40% (GLC). The ratio of
the cis and trans isomers of the starting compound
before and after reaction is almost the same (56:44,
respectively), implying comparable reactivity of both
the isomers in the reaction in question. The reaction
probably involves Al O coordination bond forma-
tion followed by C O bond cleavage [4]. The absence
of boron derivatives in the organic phase suggests
formation of aluminum salts of boric or metaboric
acids or their hydrolysis products. Thus, the configura-
tional differences in the aliphatic part of the 1,3,2-di-
oxaborinane ring here exert almost no effect on pro-
cesses involving the heteroatomic molecular fragment.
(over the course of 30 min) with stirring at room
temperature to 0.01 mol of ester I in 100 ml of
benzene, after which the mixture was heated under
reflux for 1 h on a water bath and poured onto ice.
The organic phase was separated, the aqueous phase
was treated with benzene (2 50 ml), the combined
organic extracts were concentrated on a rotary eva-
porator, and the residue was subjected to GLC
analysis.
The configurational assessment of the isomers of
ester I has been described in [5, 6]. Gas chromato-
graphy was performed on a Tsvet-126 chromatograph
with a flame-ionization detector, column 3000 4 mm,
stationary phase 5% OV-17 on Chromaton N-Super,
carrier gas argon.
Anhydrous AlBr3, 0.01 mol, was added slowly
1070-3632/01/7106-0987$25.00 2001 MAIK Nauka/Interperiodica
Kuznetsov
