Tetrahedron Letters
Copper-catalyzed diesterification of 1,3-diene for the synthesis
of allylic diester compounds
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Bo Qian, Haigen Xiong, Nengbo Zhu, Changqing Ye, Wujun Jian, Hongli Bao
Key Laboratory of Coal to Ethylene Glycol and Its Related Technology, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, 155 Yangqiao Road
West, Fuzhou 350002, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
A novel and atom economical copper-catalyzed diesterification of 1,3-dienes has been developed; the
available allylic diester derivatives, which are the important intermediates for the synthesis of natural
products, were attained with moderate to good yields. Preliminary mechanistic study suggests that allylic
radical might be involved in this transformation.
Received 19 May 2016
Revised 15 June 2016
Accepted 20 June 2016
Available online 21 June 2016
Ó 2016 Elsevier Ltd. All rights reserved.
Keywords:
Diesterification
1,3-Dienes
Aryl diacyl peroxide
Allylic diester
Allylic radical
Difunctionalization of isolated alkenes is one of classic and
valuable transformations known in organic synthesis.1 Particularly,
numerous metal mediated and metal catalyzed difunctionalization
reactions in the field have been developed broadly including
alkene dioxygenation,2 aminooxygenation,3 diamination,4 diaryla-
tion5 and aminohalogenation.6 Comparison with isolated alkenes,
the catalytic difunctionalization of conjugated dienes has received
significantly less attention.7 Shi developed a series of important
palladium and copper catalyzed diamination reactions of 1,3-
dienes.8 Diarylation and 1,2-hydrovinylation of 1,3-dienes under
palladium catalysis were recently reported by Sigman.9 Addition-
ally, the functionalization of 1,3-dienes was also successfully
employed in catalytic [4+2] cycloaddition.10 Mechanistically, palla-
dium-catalyzed difunctionalization of conjugated dienes generally
To our knowledge, a more general method for the copper-cat-
alyzed diesterification of 1,3-dienes to the corresponding allylic
diester derivatives has not been demonstrated to date. Further-
more, the allylic diester derivatives could transform to diol deriva-
tives which are key in the synthesis of natural products.13 We
herein established a new and atom economical synthetic approach
for diesterification of 1,3-dienes with aryl diacyl peroxide using
copper as catalyst under mild reaction conditions.
The copper-catalyzed 1,2-alkylesterification of dienes was real-
ized in our previous work and only 11% yield of the 1,2-arylesterifi-
cated product was generated in the presence of catalytic amounts of
CuTc when employing benzoyl peroxide and 2,3-dimethylbuta-1,3-
diene.12 However, the 1,2-diesterificated product could be obtained
with 40% yield using 10 mol% of CuTc as catalyst in 1,4-dioxane at
80 °C for 18 h (Table 1, entry 1). With this result in hand, we con-
ducted the reaction condition optimization while 2,3-dimethyl-
buta-1,3-diene 1a and benzoic peroxide 2a were determined as
the model substrates. Initially, the yield of 1,2-diesterificated pro-
duct 3a was increased to 55% in toluene with CuTc as catalyst
(Table 1, entry 2). The catalyst screening in toluene revealed that
CuBr was the most reactive catalyst for this transformation com-
pared to other copper catalysts, improving the yield further to 63%
(Table 1, entry 5). Examination of solvent showed that 1,2-
dichlorobenzene was the best solvent, which led to an improvement
of anticipated product in 72% yield (Table 1, entry 7). Moreover, the
yield of product 3a declined with decreasing the reaction tempera-
ture from 80 °C to 60 °C (Table 1, entry 7–9). Decreasing CuBr
proceeds through the generation of
ates from Pd(0) or Pd(II) with 1,3-dienes.11 (Scheme 1a) However,
besides the formation of -allyl metal species, copper catalyzed
p-allyl palladium intermedi-
p
difunctionalization of 1,3-dienes is likely to be undergoing an
allylic radical pathway.7a,8g Recently, our laboratory contributed a
regioselective 1,2-alkylesterification of dienes to allylic esters in
the presence of copper catalyst, in which we proposed that 1,3-
dienes reacted with alkyl radical to afford allylic radical
intermediates and subsequently coupled with other partners12
(Scheme 1b).
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Corresponding author.
0040-4039/Ó 2016 Elsevier Ltd. All rights reserved.