Palladium catalyzed regioselective elimination-hydrocarbonylation of propargylic alcohols

Article abstract of DOI:10.1039/c9cc03262b

A straightforward approach to synthesizing substituted 1,3-alkadien-2-yl carboxylic acids starting from readily available propargylic alcohols was developed. Based on mechanistic studies, the reaction was found to proceed via regioselective hydrocarbonylation of the C-C triple bonds of the in situ formed 1,3-enyne intermediates, providing 1,3-alkadien-2-yl carboxylic acids with a very high selectivity.

Full text of DOI:10.1039/c9cc03262b

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Marilyn M. Olmstead, Alan L. Balch, Josep M. Poblet, Luis Echegoyenet al.
Reactivity differences of Sc3N@C2n (2n 68 and 80). Synthesis of the
first methanofullerene derivatives of Sc N@D5h-C80
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DOI: 10.1039/C9CC03262B
Journal Name
COMMUN
Palladium Catalyzed Regioselective Elimination-
Hydrocarbonylation of Propargylic Alcohols
Yuan Yuan,a Minqiang Jia,a Wanli Zhang,*a and Shengming Ma*a,b
Received 00th January 20xx,
Accepted 00th January 20xx
DOI: 10.1039/x0xx00000x
www.rsc.org/
A straightforward approach to substituted 1,3-alkadien-2-yl reversed regioselectivity-a highly selective atom-economic
carboxylic acids starting from readily available propargylic alcohols approach to afford A-type 1,3-alkadien-2-yl carboxylic acids
was developed. Based on mechanistic studies, the reaction was from readily available tertiary 2-alkynylic alcohols under 1 atm
found to proceed via regioselective hydrocarbonylation of the C-C of CO (Scheme 1d).
triple bonds of the in situ formed 1,3-enyne intermediates
providing 1,3-alkadien-2-yl carboxylic acids with a very high
selectivity.
CO -based
2
(a) Non-selective
R2
Ni-catalyzed hydrocarbonylation of 1,3-enynes
R3
R2
R3
R4
R2
1) Ni catalyst
2) H3O+, 20 o
R1
R1
R1
CO2
5 atm
+
+
R3
R4
C
R4
H
H
OOC
H
H
COO
A
type B
type
1,3-Dienes are important building blocks in organic synthesis
and material sciences due to their wide existence in natural
products and their utility in Diels-Alder reactions.1 In particular,
1,3-alkadienes with an electron-deficient carboxylic acid or
ester group in different location have received much
attention.2,3 The syntheses of B-type 2,4-alkadienoic acids have
been well-established.2 In contrast, A-type 1,3-alkadien-2-yl
carboxylic acids were usually prepared via Wittig reaction of
aldehydes,3a carbonylation of 2,3-dien-1-ols,3b and addition-
elimination of 3-(methoxycarbonyl)-1,2-allen-4-ols3c. In
addition, Ni-catalyzed CO2-based hydrocarboxylation of 1,3-
enynes affords a isomeric mixture of these two types of
products (Scheme 1a).4 On the other hand, propargylic alcohols
are readily available chemicals and the corresponding
carbonylation reactions may afford 2-hydroxylacrylic acids,
dicarbonylation products, lactones, and 2,3-allenoic acids.5,6 Of
particular interest, Alper and coworkers disclosed that the
carbonylation of terminal alkynols leads to the selective
formation of 2,4-alkadienoic acids (Scheme 1b).7 We recently
reported a hydroxy group-enabled linear-selective hydro-
esterification reaction of alkynes, affording 3-hydroxy-2(E)-
alkenoates (Scheme 1c).5g Here we present an unexpected
elimination-hydrocarbonylation of propargylic alcohols with a
35/65 to 90/10 branch/linear selectivity
CO-based
(b) Pd-catalyzed
hydrocarbonylation of tertiary terminal 2-alkynols
R2
R1
R2 R1
HO
-
[(Cy3P)Pd(H)(H2O)]+BF4
+
CO
dppb, p-TsOH, THF
20 atm
100 oC, 48 h
H
COOH
B
type (59-92%)
(c) Our previous work: Hydroxy group-enabled regioselectivity control
H
O
R
Pd(TFA)2 (4 mol%)
Ligand (6 mol%)
ROH (8.0 equiv.)
H
COOR
H
H
COOR
O
Predictable
R3
R1
R2
R2
R3
R1
R2
Dehydration Product
Toluene (5.0 mL)
R1
R4
OH
balloon, T oC
CO
B
type
(d) This work: Mechanism-dependent reversed regioselectivity
H
COOH
cat. Pd
CO
H
H
O
H2O,
R2
R2
Ar R2
(PhO)2POOH
Ar
Ar
A
type (40-85%)
15 examples
Scheme 1. Approaches to A- and B-types of 1,3-alkadienyl carboxylic acids or
esters
During our investigation on carbonylation of 2-phenyloct-3-
yn-2-ol 1a to afford 2,3-allenote,8 1,3-enyne 2a was found to be
a byproduct. In the absence of methanol, when we increased
the amount of (PhO)2POOH to 0.5 equiv., no enyne 2a was left
and (E)-1,3-dien-2-yl carboxylic acid (E)-3a with a branched
selectivity and 2,4-alkadienoic acid (E)-4a6 with a linear
selectivity was obtained in 66% and 5% yields, respectively
(Table 1, entry 1). The regioselectivity is reversed as compared
to what is shown in Scheme 1d.7 When PPh3 was applied, 18%
yield of (E)-3a and 5% yield of (E)-4a were detected, together
with 9% yield of dehydration product 1,3-enyne 2a (Table 1,
entry 2). When DPPM was used, 58% yield of enyne 2a was
detected and only 3% yield of the product (E)-3a was generated
(Table 1, entry 3). In contrast, DPPB offered 39% yield of (E)-3a,
a. Research Center for Molecular Recognition and Synthesis, Department of
Chemistry, Fudan University, 220 Handan Lu, Shanghai 200433, P. R. China.
b. State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic
Chemistry, Chinese Academy of Sciences, 345 Lingling Lu, Shanghai 200032, P. R.
China. E-mail: masm@sioc.ac.cn.
Electronic Supplementary Information (ESI) available: [details of any supplementary
information available should be included here]. See DOI: 10.1039/x0xx00000x
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 1
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10% yield of (E)-4a, and 15% yield of 1,3-enyne 2a (Table 1, aryl, and hydrogen (Table 2, entries 1-8). This aryl group may be
View Article Online
entry 4). Commercially available bisphosphine ligands such as substituted with halogen, methyl, aDnOdI: 1m0.1e0t3h9o/Cxy9CCa0t32t6h2Be
DPEphos, DPPF, and BIPHEP were then tested, demonstrating meta/para position (Table 2, entries 10-14). 2-Naphthyl was
that BINAP is the optimal ligand (Table 1, entries 5-7). Then also tolerated (Table 2, entry 15). The configuration of the C=C
different palladium precursors such as PdCl2, Pd(PPh3)Cl2, bond in (E)-3a was further established by X-ray diffraction study
Pd(dppf)Cl2, Pd(TFA)2, Pd(acac)2, and Pd(PPh3)4 were screened, (Scheme 2).9
however, they all gave inferior results (Table 1, entries 8-13).
Table 2. Scope studiesa
Table 1. Optimization of reaction conditionsa
[PdCl(-allyl)]2 (2 mol%)
BINAP (6 mol%)
(PhO)2POOH (1.5 equiv.)
COOH
[Pd(-allyl)Cl]2 (2 mol%)
BINAP (6 mol%)
(PhO)2POOH (0.5 equiv.)
HO
Ar
H
R
COOH
H
H
HO
Ph
Toluene, 80 oC, 12 h
CO balloon
n-Bu
+
n-Bu
Ar
(E)-
+
R
Toluene, 80 oC, 12 h
CO balloon
Ph
COOH
Ph
Ph
3
1
n-Bu
n-Bu
4a
1a
2a
3a
(E)-
Branched
(E)-
Linear
Yield of 3(%)
Entry
Ar
R
Product
b
NMR yield (%) b
Changes from the conditions
shown in the equation
none
Recovery
of 1a (%) b
Entry
1
1
2
3
4c
5
6d
7e
8f
9g
10
11
12
13
14
15
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
n-Bu
-(CH2)4Cl
-(CH2)2Ph
i-Pr
H
Ph
3-MeC6H4
4-ClC6H4
Ph
n-Bu
n-Bu
n-C6H13
n-C6H13
n-C6H13
n-C6H13
3a
3b
3c
3d
3e
3f
3g
3h
3i
3j
3k
3l
3m
3n
3o
82
85
76
80
47
58
40
48
51
69
40
73
74
76
75
2a
0
9
58
15
5
0
5
21
34
59
0
0
0
0
0
0
0
0
0
3a
66
18
3
39
25
43
50
32
21
4
64
51
20
81
79
84
83
46
48
4a
5
5
0
10
0
12
10
1
1
0
7
0
0
1
1
0
0
0
3
7
0
5
22
9
5
2
0
0
3
6
6
1
1
0
0
0
0
c
2
PPh3as the ligand
DPPM as the ligand
DPPB as the ligand
DPEphos as the ligand
DPPF as the ligand
3
4
5
6
7
BIPHEP as the ligand
PdCl2 as the precursor
Pd(PPh3)2Cl2 as the precursor
Pd(dppf)Cl2 as the precursor
Pd(TFA)2 as the precursor
Pd(acac)2 as the precursor
Pd(PPh3)4 as the precursor
1.0 equiv. (PhO)2POOH
1.0 equiv. (PhO)2POOH
1.5 equiv. (PhO)2POOH
2.0 equiv. (PhO)2POOH
1.5 equiv. (PhO)2POOH
1.5 equiv. (PhO)2POOH
8d
4-ClC6H4
4-ClC6H4
4-MeC6H4
4-BrC6H4
3-MeC6H4
3-MeOC6H4
2-Naphthyl
9d
10d
11d
12d
13d
14
15e
16e
17e
18e,f
19e,g
a Reaction conditions: 1 (1.0 mmol), [(π-allyl)PdCl]2 (2 mol%), BINAP (6 mol%), and
(PhO)2POOH (1.5 equiv.) in toluene (5.0 mL) at 80 oC under 1 atm of CO unless
otherwise noted. b Isolated yield. c The reaction was carried out for 30 h; 10% enyne
was detected. d The reaction was carried out for 42 h. e 29% enyne was detected. f
14% enyne was detected. g The reaction was carried out for 24 h.
0
a Reaction conditions: 1a (0.5 mmol), [(π-allyl)PdCl]2 (2 mol%), ligand (6 mol%), and
(PhO)2POOH (0.5 equiv.) in toluene (2.5 mL) at 80 oC under 1 atm of CO unless
b
otherwise noted. Determined by 1H NMR analysis of the crude product using
dibromomethane as the internal standard. c PPh3 (12 mol%) was used. d [Pd] (4
COOH
H
f
mol%) was used. e The reaction was conducted on 1.0 mmol scale. The reaction
was conducted under 5 atm of CO. g The reaction was conducted under 10 atm of
CO.
n-Bu
Ph
3a
(E)-
Scheme 2. The ORTEP representation of (E)-3a
When the loading of (PhO)2POOH was improved to 1.0
equivalent, the yield of the branched product (E)-3a was
improved dramatically with an excellent regioselectivity (Table
1, entry 14). The reaction was then carried out on 1 mmol scale
with no obvious decline in yield (Table 1, entry 15). We further
increased the loading of (PhO)2POOH to 1.5 equivalent and
found that the branched product (E)-3a was formed exclusively
with an increased yield of 84% (Table 1, entry 16). When the
loading of (PhO)2POOH was increased to 2.0 equivalent, no
further improvement was observed (Table 1, entry 17). The
influence of CO pressure was then examined and similar low
yield was achieved under 5 or 10 atm of CO (Table 1, entry 18,
19). Thus, reaction conditions of entry 16 in Table 1 were chosen
as the optimal conditions.
To shed light on the mechanism, the reaction was monitored
using substrate 1a (See supporting information for the details).
It illustrated that enyne 2a emerged at the very beginning of the
process and then it was slowly transformed to the
hydrocarbonylation product (E)-3a (Scheme 3).
With the optimized reaction conditions in hand, the substrate
scope was then evaluated (Table 2). When aryl (Ar) is phenyl
group, R may be 1-alkyl, 4-chlorobutyl, 2-phenylethyl, isopropyl,
2 | J. Name., 2012, 00, 1-3
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phosphoric acid with Pd(0) gives rise to Pd-H species Int A.11
View Article OTnlhinee
loading of phosphoric acid assisted theDdOeI:h1y0d.1r0a3t9i/oCn9CoCf0132a62toB
form 1,3-enyne 2a. Subsequent insertion of C-C triple bond in
2a to the Pd-H bond in intermediate Int A would give
intermediate Int B. The aryl group may account for the observed
regioselectivity. Then CO insertion in the presence of water
would afford intermediate Int C. Reductive elimination would
yield product (E)-3a and regenerate Pd(0) to complete the
catalytic cycle.
100
100
50
0
80
60
40
20
0
Enyne 2a
Product 3a
0
2
4
6
8
10
Reaction Time (h)
HOOP(OPh)2
HO
Scheme 3. Reaction profile by monitoring of 2a and (E)-3a
n-Bu
Ph
1a
(PhO)2POOH
Pd(0)L2
A couple of control experiments were also conducted to
provide further insights into the mechanism (Scheme 4): (1)
when 1,3-enyne 2a was prepared and subjected to the
optimized conditions, product (E)-3a was generated with a
similar yield, further proving that 2a is the intermediate
(Scheme 4a); (2) when 2-phenyloct-3-yn-2-yl methyl ether 5
was applied, the corresponding dienoate (E)-6 was also formed
in high yield (Scheme 4b). (3) Interestingly, when 2-methyloct-
3-yn-2-ol 1p was used, B-type linear product (E)-4p was formed
instead (Scheme 4c), disclosing that the regioselectivity is
substrate dependent; (4) When 3-phenylnon-4-yn-3-ol 1q was
applied, 59% yield of (Z)-3-phenyl-2-nonen-4-yne (Z)-2q10 and
19% yield of hydrocarbonylation product [2E,2-(1Z)]-3q was
isolated(Scheme 4d); (5) Direct application of (Z)-2q also led to
the formation of [2E,2-(1Z)]-3q in 25% yield, indicating that the
steric effect at C=C bond side has an influence on the reaction
yield but it will not affect the regioselectivity (Scheme 4e).
OPO(OPh)2
PdL2
Int A
H2O
H
COOH
H
n-Bu
Ph
Ph n-Bu
3a
2a
(E)-
O
(PhO)2OPO
L2Pd
PdL2
H
OH
H
Ph
Ph
n-Bu
Int C
n-Bu
Int B
(PhO)2POOH
CO + H2O
Scheme 5. Proposed mechanism
The reaction of 2-(4-bromophenyl)dec-3-yn-2-ol 1l was then
conducted on 5 mmol scale, providing the corresponding
branched product (E)-3l in 1.3016 g without obvious decline in
yield (Scheme 6).
[PdCl(-allyl)]2 (2 mol%)
BINAP (6 mol%)
(PhO)2POOH (1.5 equiv.)
COOH
H2O (8.0 equiv.)
H
(a)
(b)
n-Bu
Ph
Toluene, 80 oC, 12 h
CO balloon
Ph n-Bu
COOH
[PdCl(-allyl)]2 (2 mol%)
2a
3a
(E)-
80% yield
HO
H
BINAP (6 mol%)
(PhO)2POOH (1.5 equiv.)
n-C6H13
n-C6H13
[PdCl(-allyl)]2 (2 mol%)
BINAP (6 mol%)
(PhO)2POOH (1.5 equiv.)
Toluene, 80 oC, 12 h
CO balloon
COOMe
MeO
Ph
H
Br
Br
n-Bu
Toluene, 80 oC, 12 h
CO balloon
3l
Ph n-Bu
1l
5 mmol
(E)-
5
77% yield
1.3016 g
6
(E)-
78% yield
Scheme 6. Gram scale reaction
[PdCl(-allyl)]2 (2 mol%)
BINAP (6 mol%)
H
HO
(PhO)2POOH (0.5 equiv.)
COOH
(c)
n-Bu
To illustrate the usefulness of this product, several
transformations were conducted (Scheme 7): (1) When (E)-3l
was firstly transformed to ester, it could react with(3-
nitrophenyl)boronic acid to give the Suzuki coupling product
(E)-7 in 80% yield;12 (2) When treated with DIBAL-H, the
corresponding alcohol (E)-8 was obtained in 60% yield; (3)
Aldehyde (E)-9 can also be obtained in 58% yield after (E)-3l was
transformed into the Weinreb amide,13 followed by reduction
with LiAlH4.
Toluene, 80 oC, 12 h
CO balloon
Me n-Bu
1p
4p
(E)-
42% yield
[PdCl(-allyl)]2 (2 mol%)
BINAP (6 mol%)
(PhO)2POOH (1.5 equiv.)
COOH
HO
Et
Ph
H
(d)
n-Bu
+
n-Bu
Toluene, 80 oC, 12 h
CO balloon
Ph
Ph n-Bu
3q
1q
2q
(Z)-
[2E,2-(1Z)]-
19% yield
59% yield
[Pd(-allyl)Cl]2 (2 mol%)
BINAP (6 mol%)
(PhO)2POOH (1.5 equiv.)
H2O (8.0 equiv.)
COOH
H
(e)
n-Bu
Ph
Toluene, 80 oC, 12 h
CO balloon
Ph
n-Bu
2q
(Z)-
3q
[2E,2-(1Z)]- , 25% yield
2q
58% recovery of (Z)-
Scheme 4. Control experiments
Based on the above results, a plausible mechanism for the
formation of 3a is proposed (Scheme 5): Oxidative addition of
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1083-1090; (b) M. Baumann and W. Hoffmann, Synthesis,
View Article Online
COOMe
H
1977, 1977, 681-682; (c) K. Tanaka, M. Terauchi and A. Kaji,
Chem. Lett., 1981, 10, 315-318; (d) J. ID. OI.I:K1i0m.1,0B39. /AC.9PCaCt0e3l2a6n2dB
R. F. Heck, J. Org. Chem., 1981, 46, 1067-1073; (e) S. Tsuboi,
T. Masuda and A. Takeda, J. Org. Chem., 1982, 47, 4478-4482;
(f) T.-a. Mitsudo, S.-W. Zhang, M. Nagao and Y. Watanabe, J.
Chem. Soc., Chem. Commun., 1991, 598-599; (g) C. Guo, X. Lu,
Tetrahedron Lett., 1992, 33, 3659-3662; (h) C. Fu and S. Ma,
Org. Lett., 2005, 7, 1707-1709; (i) M. Liu, P. Yang, M. K.
Karunananda, Y. Wang, P. Liu and K. M. Engle, J. Am. Chem.
Soc., 2018, 140, 5805-5813.
n-C6H13
1) H2SO4, MeOH, reflux, 7 h, 81%
2) 3-NO2-C6H4B(OH)2 (1.0 equiv.)
Pd(dppf)Cl2 (10 mol%)
NO2
K2CO3 (2 equiv.)
DMSO, 80 oC, 2 h, 80% yield
7
(E)-
3
For selected works on 1,3-Alkadien-2-yl carboxylic acids, see:
(a) H. Hoffmann, J. Rabe, Angew. Chem., Int. Ed. Engl., 1983,
22, 795-796; (b) J. Nokami, A. Maihara and J. Tsuji,
Tetrahedron Lett., 1990, 31, 5629-5630; (c) Y. Deng, X. Jin, and
S. Ma, J. Org. Chem., 2007, 72, 5901-5904.
CH2OH
H
COOH
H
n-C6H13
1) H2SO4, MeOH, reflux, 7 h, 81%
n-C6H13
2) DIBAL-H (2 equiv.), toluene
-78 oC 3 h to r.t. 4 h, 60% yield
4
5
S. Derien, J. C. Clinet, E. Dunach and J. Perichon, J. Organomet.
Chem., 1992, 424, 213-224.
Br
Br
8
(E)-
(a) R. W. Rosenthal, L. H. Schwartzman, N. P. Greco, R. Proper,
J. Org. Chem., 1963, 28, 2835-2838; (b) T. Nogi and J. Tsuji,
Tetrahedron, 1969, 25, 4099-4108; (c) K. Matsushita, T.
Komori, S. Oi and Y. Inoue, Tetrahedron Lett., 1994, 35, 5889-
5890; (d) F. Pascali and G. Chiusoli, J. Chem. Soc., Perkin
Transactions 1, 1997, 147-154; (e) W.-Y. Yu and H. Alper, J.
Org. Chem., 1997, 62, 5684-5687; (f) C. S. Consorti, G. Ebeling
and J. r. Dupont, Tetrahedron Lett., 2002, 43, 753-755; (g) C.
Huang, H. Qian, W. Zhang and S. Ma, Chem. Sci., 2019, 10,
5505-5512.
3l
(E)-
CHO
1) MeNHOMe•HCl (1.05 equiv.)
4-DMAP (0.05 equiv.)
DCC (1.05 equiv.)
Et3N (2.0 equiv.)
CH2Cl2, r.t., 24 h, 47%
H
n-C6H13
2) LiAlH4 (1.20 equiv.)THF
-78 oC, 0.5 h, 56% yield
Br
9
(E)-
Scheme 7. Synthetic applications of 1,3-alkadien-2-yl carboxylic acids
6
7
For the X-ray structure of (E)-4a, see: W.-F. Zheng, W. Zhang,
J. Huang, Y. Yu, H. Qian and S. Ma, Org. Chem. Front., 2018, 5,
1900-1904.
(a) K. T. Huh, A. Orita and H. Alper, J. Org. Chem., 1993, 58,
6956-6957; (b) B. El Ali, and H. Alper, J. Mol. Catal. A: Chem.,
1995, 96, 197-201.
In conclusion, a palladium-catalyzed efficient synthesis of 1,3-
alkadien-2-yl carboxylic acids through regioselective
hydrocarbonylation of the in situ generated conjugated 1,3-
enynes from readily available propargylic alcohols in the
presence of CO was established. (PhO)2POOH was found to be
the key additive for two steps in this transformation. Synthetic
potential leading to other useful building blocks was also
demonstrated. Further studies in this area are being conducted
in our laboratory.
8
9
W. Zhang, C. Huang, Y. Yuan and S. Ma, Chem. Commun., 2017,
53, 12430-12433.
The structure of (E)-3a was confirmed by single-crystal X-ray
diffraction analysis. CCDC 1582245 contains the
supplementary crystallographic data for compound (E)-3a.
Crystal data for compound (E)-3a: C15H18O2, MW = 230.29,
monoclinic, space group I2/a, final R indexes [I > 2σ(I)], R1 =
0.0719, wR2 = 0.2203; R indexes (all data), R1 = 0.0759, wR2 =
0.2259, a = 8.7690(2) Å, b = 17.0752(4) Å, c = 18.1342(3) Å, α
= 90o, β = 89.897(2)o, γ = 90o, V = 2715.27(10) Å3, T = 293(2) K,
Z = 8, reflections collected/unique 29293/2375 [Rint = 0.0773],
no. of observations [> 2σ(I)] 2120, parameters: 156.
ACKNOWLEDGMENTS
Financial supports from the National Natural Science
Foundation of China (Grant No. 21690063) are greatly
appreciated. We also thank Mr. Haibo Xu in this group for
reproducing the results for (E)-3d, (E)-3g, and (E)-3o presented
in Table 2.
10 The structure of (Z)-2q was determined by comparing with
literature: M. Callingham, B. M. Partridge, W. Lewis and H. W.
Lam, Angew. Chem. Int. Ed., 2017, 129, 16570-16574.
11 For a review on Pd-H involved mechanism, see: (a) A.
Brennführer, H. Neumann and M. Beller, ChemCatChem 2009,
1, 28-41; For a report, see: (b) D. L. Reger and D. G. Garza,
Organometallics, 1993, 12, 554-558.
Conflicts of interest
There are no conflicts to declare.
12 N. Miyaura, T. Yanagi and A. Suzuki, Synth. Commun., 1981,
11, 513-515.
13 (a) S. Nahm, S. M. Weinreb, Tetrahedron Lett., 1981, 22, 3815-
3818; (b) I. Iriarte, O. Olaizola, S. Vera, I. Gamboa, M. Oiarbide
and C. Palomo, Angew. Chem. Int. Ed., 2017, 56, 8860-8864.
Notes and references
1
For selected books, see: (a) W. Oppolzer, in Comprehensive
Organic Synthesis, ed. I. Fleming, Pergamon, Oxford, 1991, pp.
315-399; (b) W. R. Roush, in Comprehensive Organic Synthesis,
ed. I. Fleming, Pergamon, Oxford, 1991, pp. 513-550; (c) G.
Mehta and P. Rao, In The Chemistry of Dienes and Polyenes,
ed. Z. Rappoport, John Wiley & Sons: 1997, pp 361-467; (d) F.
Fringuelli and A. Taticchi, The Diels-Alder reaction: selected
practical methods. John Wiley & Sons: 2002.
2
For selective representative works on 2,4-alkadienoic acids,
see: (a) H. A. Dieck and R. F. Heck, J. Org. Chem., 1975, 40,
4 | J. Name., 2012, 00, 1-3
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DOI: 10.1039/C9CC03262B
[PdCl(-allyl)]2 (2 mol%)
BINAP (6 mol%)
COOH
HO
Ar
(PhO)2POOH (1.5 equiv.)
H
R
Toluene, 80 oC, 12 h
CO balloon
Ar
A
R
type (40-85%)
15 examples
Substituted 2-aryl-1,3-alkadien-2-yl carboxylic acids were formed from readily available
propargylic alcohols via a dehydration-carboxylation process.