DOI: 10.1002/chem.201204039
Rhodium-Catalyzed Carbocyclization and Chlorosulfonylation of 1,6-Enynes
with Sulfonyl Chlorides
Chen Chen, Jianhua Su, and Xiaofeng Tong*[a]
The transition-metal catalyzed cyclization of enyne has
been one of the most efficient methods for the synthesis of
various types of cyclic compounds.[1] The metal-catalyzed ad-
dition–carbocyclization reactions[2] of 1,6-enyne with re-
our continuous research on the catalytic cyclization of 1,6-
enynes,[8] we herein report the first example of the RhI-cata-
lyzed carbocyclization and chlorosulfonylation of 1,6-enynes
with sulfonyl chlorides as a linker, in which three different
À
À
À
À
À
agents containing interheteroatom X Y bonds [X Y=
metal–metal reagent (B, Si, Ge, Sn, etc.),[3] metal–H re-
agent,[4] dihalogen[5]] constitute synthetically highly versatile
bonds, C Cl, C C, and C S, are efficiently formed with
high regioselectivity and stereoselectivity (Scheme 1b).
We started our investigation by screening different metal
catalysts for the carbocyclization and chlorosulfonylation re-
action of 1,6-enyne 1a (1 equiv) with TsCl 2a (1.5 equiv).[9]
Whereas most of the tested catalysts, including CuCl, [Fe-
À
processes, which furnish the formation of a new C C bond
À
À
along with C X and C Y bonds in a one-step fashion and
represent a facile route to carbocyclic and heterocyclic ring
systems (Scheme 1a). Although related reactions have been
A
ACHTUGNRTNE(NUNG PPh3)2Cl2], showed no activity for the at-
AHCTUNGTRENNUNG
enable the complete consumption of 1a, although a compli-
cated reaction resulted (Table 1, entry 1). Fortunately, com-
Table 1. Optimization of reaction conditions.[a]
Scheme 1. Metal-catalyzed addition–cyclization of 1,6-enyne.
extensively investigated recently, their power and scope is
ultimately impeded by the limitation of the above-men-
tioned linkers; no other type of s-bond linkers, to the best
of our knowledge, have been reported. Therefore, the devel-
opment of novel linkers for the addition–carbocyclization
reactions, especially under the guidance of novel reaction
mechanism(s), is still highly desirable.
Recent discoveries have heralded a renaissance for sulfon-
yl chlorides as readily available, inexpensive, and versatile
reagents for metal-catalyzed transformations.[6] It occurred
to us that sulfonyl chlorides might serve as a novel linkers
for catalytic addition–carbocyclization reactions. In fact, the
addition of sulfonyl chlorides across terminal alkynes has
been successfully achieved with the assistance of Cu or Fe
complexes,[7] demonstrating their similar potential[2] as for
the above mentioned element–element linkers. As part of
Entry
x
[Rh]
L
Additive
Yield[b]
[%]
[c]
[c]
1
2
3
4
5
6
7
8
1.5
1.5
1.5
1.5
1.5
1.5
2.0
2.5
[Rh
[Rh
[Rh
[Rh
[Rh
[Rh
[Rh
[Rh
G
–
–
–
6
[c]
R
LiCl–H2O[d]
LiCl–H2O
LiCl–H2O
LiCl–H2O
LiCl–H2O
LiCl–H2O
LiCl–H2O
43
77
42
26
30
83
92
E
DPPF
DPPE
DPPP
DPPB
DPPF
DPPF
AHCTUNGTRENNUNG
AHCTUNGTRENNUNG
AHCTUNGTRENNUNG
AHCTUNGTRENNUNG
AHCTUNGTRENNUNG
[a] Reaction conditions: enyne
(0.02 mmol), ligand (0.022 mmol), 3 mL dioxane. [b] Yield of isolated
product. [c] Without ligand or additive. [d] 1.0 equiv LiCl–H2O was used.
1
(0.2 mmol), catalyst precursor
pound 3aa was indeed obtained, albeit only in 6% yield
after very careful chromatography. The structure of 3aa was
unambiguously determined by X-ray diffraction analysis
(Figure 1, left).[10] The (E)-configuration of exo-double bond
in 3aa implied that the chloride might attack the triple bond
of 1a from the opposite direction of alkyne–rhodium com-
plex (see below). Indeed, the addition of LiCl–H2O
(1 equiv) significantly improved the reaction performance,
leading to the isolation of 3aa in 43% yield (Table 1,
entry 2). These promising results promted us to test the
[a] C. Chen, Prof. J. Su, Dr. X. Tong
Shanghai Key Laboratory of Functional Materials Chemistry
East China University of Science and Technology
Meilong Road, 130, Shanghai 200237 (P.R. China)
Fax : (+86)21-64253881
Supporting information for this article is available on the WWW
5014
ꢁ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2013, 19, 5014 – 5018