Tetrahedron Letters
DBSA-catalyzed Friedel–Crafts alkylation of cyclic ketene
dithioacetals with alcohols in water
Haifeng Yu , Peiqiu Liao b
a,
⇑
a
School of Chemistry and Life Science, Anshan Normal University, Anshan, Liaoning 114007, China
Department of Chemistry, Northeast Normal University, Changchun, Jilin 130024, China
b
a r t i c l e i n f o
a b s t r a c t
Article history:
A novel DBSA-catalyzed Friedel–Crafts alkylation of cyclic ketene dithioacetals, internal alkenes with
highly nucleophilic carbon atom adjacent to the electron-withdrawing group, with alcohols in water
has been developed. The reaction is efficient in the presence of catalyst loading as low as 10 mol % in
water at reflux, and a wide range of alkylated ketene dithioacetals are synthesized in excellent yields.
Ó 2016 Elsevier Ltd. All rights reserved.
Received 31 March 2016
Revised 16 May 2016
Accepted 17 May 2016
Available online xxxx
Keywords:
Dodecylbenzenesulfonic acid
Olefins
Ketene dithioacetals
Alcohols
Friedel–Crafts alkylation
Introduction
A Friedel-Crafts alkylation of arenes and heteroarenes in water
1
) DBSA (10 mol%) 5
2) calyx[6] arene-SO
H 6
) Au(III)/TPPMS (2 mol%)
H O
Over the past decade, organic reaction in water without the use
of organic solvents is regarded as an important research topic in
green chemistry since the use of water can remarkably reduce
3
OH
Ar2
7
Ar
3
Ar
+
Ar1
Ar1
Ar2
2
1
the discharge of harmful organic solvents. Friedel–Crafts alkyla-
B Friedel-Crafts alkylation of cyclic ketene dithioacetals in water
tion is one of the most prominent C–C bonds-forming reactions,
and has been widely applied in the synthesis of many natural prod-
R
1
EWG
S
EWG
S
2
R2
OH
R2
ucts and biologically active compounds. Among them, the alkyla-
DBSA (10 mol%)
H O, reflux
+
tion of alcohols as green alkylating reagents has attracted
considerable attention because water is the exclusive by-product,
R1
S
2
S
(
)n n=1,2
( )nn=1,2
3
1
2
3
which establishes an environmentally benign alkylation process.
Friedel–Crafts alkylation of arenes or heteroarenes with alcohols
Scheme 1. Friedel–Crafts alkylation in water.
4
had been well documented in the past years, and their alkylations
5
catalyzed by dodecylbenzenesulfonic acid (DBSA), calyx[6] arene
bond.8 Recently, the high nucleophilic nature of ketene dithioac-
etals grabbed the attention for the alkylations with alcohols
6
7
sulfonic acids, or Au(III)/TPPMS in water have been realized suc-
cessfully in recent years (Scheme 1A). Nevertheless, the letters on
the alkylation of olefins with alcohols are rare, owing to the lower
nucleophilicity.
1
3
and
BF
ÁOEt
alcohols,
dithioacetals with benzylic alcohols,
catalyzed the Friedel–Crafts alkylation between ketene
a
few letters have appeared.
These Letters include
3
2
-mediated alkylation of ketene dithioacetals with various
1
3a
CuBr
2
(30 mol %)-catalyzed alkylation of ketene
Ketene dithioacetals, which are versatile and significant
1
3b
reagents in organic synthesis,8
–12
and FeBr3 (30 mol %)-
are considered as polarized inter-
nal olefins with highly nucleophilic carbon atom adjacent to the
electron-withdrawing group (EWG) due to the push–pull effect
of the alkylthio group and the EWG at either side of the double
1
3c
dithioacetals and propargyl alcohols.
However, all the reported
reactions are performed in organic medium such as acetonitrile
and dichloromethane, which can lead to serious environmental
and safety problems. Therefore, from the green chemistry point
of view, the development of environmental compliant alkylation
of ketene dithioacetals and alcohols is a great importance and
⇑
040-4039/Ó 2016 Elsevier Ltd. All rights reserved.
0