“This document is the Accepted Manuscript version of a Published Work that appeared in final form
in [J. Am. Chem. Soc. copyright © American Chemical Society after peer review and technical editing by
the publisher. To access the final edited and published work see
https://pubs.acs.org/doi/ipdf/10.1021/jacs.7b13220.”

Ni-Catalyzed Site-Selective Dicarboxylation of 1,3-Dienes with CO2
Andreu Tortajada,† Ryo Ninokata† and Ruben Martin†§*
†Institute of Chemical Research of Catalonia (ICIQ), The Barcelona Institute of Science and Technology, Av. Països Catalans 16, 43007 Tarragona, Spain
§ ICREA, Passeig Lluïs Companys, 23, 08010, Barcelona, Spain
Supporting Information Placeholder
ABSTRACT: A site-selective catalytic incorporation of

multiple CO2 molecules into 1,3-dienes en route to adipic acids is described. This protocol is characterized by its
mild conditions, excellent chemo- and regioselectivity
and ease of execution under CO2 (1 atm), including the
use of bulk butadiene and/or isoprene feedstocks.

state-of-the-art catalytic carboxylation of olefinic C=C bonds with CO2
CO2H

“H”

H

M
path a

C
+

M
path b

CO2

single CO2
insertion

CO2H
C
single CO2
insertion

this work: site-selective multiple catalytic CO2 insertions into 1,3-dienes

The recent years have witnessed an emerging demand
for catalytic techniques that forge multiple C–C bonds
via the synergistic combination of chemical feedstocks.1
Among various conceivable scenarios, a site-selective
incorporation of carbon dioxide (CO2)2 into olefin feedstocks in the absence of stoichiometric organometallic
reagents is of particular relevance,3 holding promise to
streamline the synthesis of industrially-relevant carboxylic acids.4 Despite the elegant advances realized, these
carboxylation protocols remain currently confined to
single CO2 insertions (Scheme 1, paths a & b).5 Therefore, the ability to expand the catalytic carboxylation
portfolio of C=C bonds beyond single CO2 insertions
would be a worthwhile endeavour, opening up new
strategies for preparing saturated polycarboxylic acids.6
Scheme 1. Carboxylation of Olefinic C=C Bonds.

CO2
Ni
1,3-dienes

no “H”

L
δ–

Ni

O

I
latent
nucleophile

O

two CO2
insertions
reductant

CO2H
CO2H
chemo &
regioselective

As part of our ongoing interest in CO2,7 we questioned whether we could enable a catalytic, siteselective incorporation of multiple CO2 motifs into
abundant 1,3-dienes en route to adipic acids,8
building blocks of particular relevance in the production of plastics and adhesives.9 If successful,
this pathway might also offer an opportunity to
complement recent catalytic difunctionalization of
1,3-dienes,10 as raw materials (CO2) would be used
as electrophilic carbon synthons in lieu of nucleophilic reagents.11 However, such a scenario bears
considerable risk and might seem counterintuitive
at first sight due to (a) the proclivity of 1,3-dienes
to trigger telomerization reactions12 and (b) the fact
that statistical mixtures of monocarboxylic acids
were exclusively observed with hydrocarboxylation
conditions previously employed for either alkynes13
or alkenes, 5b reinforcing the notion that a multiple,
yet controllable, CO2 insertion event would be particularly problematic. We anticipated that a site-

selective insertion of multiple CO2 units could be
rationally controlled in the absence of hydride
sources by exploiting the inherent carbogenic nucleophilicity of I (Scheme 1, bottom).14 Upon p-s
equilibration, the targeted adipic acids could be
obtained by a subsequent regioselective CO2 incorporation into I that precedes a final reduction to
recover back the catalytic Ni(0)Ln species. Herein,
we report the successful realization of this goal,
culminating in a mild method that operates at atmospheric pressure of CO2 and is characterized by
its chemo- and regioselectivity profile, including
the ability to use of bulk butadiene and/or isoprene
feedstocks.

(entry 11) had a detrimental impact on reactivity.18
Notably, identical results were observed regardless
of whether (E)-1a or (Z)-1a were used, constituting
an additional bonus from a synthetic and practical
standpoint.19 As expected, control experiments
revealed no product formation when each parameter was omitted from the mixture (entry 12).15
Table 2. Ni-catalyzed 1,4-Dicarboxylation of 1,3-Dienes.
R3 NiBr4(TBA)2 (5 mol%)
L7 (5 mol%)
R2
R2

R1

1a-1q

CO2H

Ph
1a

Mn, CO2 (1 atm)
DMA, 50 ºC

Entry Deviation from standard conditions

CO2H
CO2H

Ph

2a

CO2H

CO2Me
R

Ph
2a’
not observed

R2

None

79, 74d

2

Using NiBr2·glyme

38, 70e

3

Using Ni(COD)2

0, 60e

4

L1 instead of L7

8

5

L2 instead of L7

46

6

L3 instead of L7

30

7

L4 instead of L7
L5 instead of L7

56

9

L6 instead of L7

33

10

DMF (NMP) as solvent

11

Zn instead of Mn

41

12

No NiBr4(TBA)2, no L7 or no Mn

0

30 (44)

N
R2

R1= R2 = H (L1)
R1 = Me; R2 = H (L2)
R1 = R2 = Me (L3)

Ph

N
R1 =

R3 =

H (L4)
R1 = R2 = H; R3 = Ph (L5)
1 = R2 = Me; R3 = Ph (L6)
R
R1 = Me; R2 = H; R3 = Ph (L7)

CO2Me

1a (0.20 mmol), NiBr4(TBA)2 (5 mol%), L7 (5 mol%),
Mn (1.50 equiv), CO2 (1 bar), DMA (0.5 M), 50 ºC. b Z/E =
1.4:1 to 5:1. c 1H-NMR yields using fluorene as internal
standard. d Isolated yield. e with TBAB (10 mol%). TBAB:
tetrabutylammonium bromide, TBA: tetrabutylammonium.

We began our investigations by studying the reaction of
1a with CO2 (1 atm). After some experimentation,15 a
cocktail consisting of NiBr4(TBA)2, L7 and Mn as
reductant in DMA at 50 ºC furnished 2a (Z/E =
2.4:1) in 74% isolated yield. It is worth noting that
not even traces of 2a’ or telomerization sideproducts were observed in the crude mixtures.
Intriguingly, the absence of ammonium salts resulted in a markedly lower reactivity (entries 2 and
3).16 A detailed survey of nitrogen-donor ligands
revealed that a seemingly trivial modification at C2
was critical for success (entries 4 vs 5-6). Unlike
recent reductive carboxylations,17 the presence of
substituents at both 2,2’-positions had a deleterious effect (entry 9 vs 1), thus showing the subtleties of our protocol. The use of other precatalysts
(entries 2 and 3), solvents (entry 10) or reductants

CO2Me

Me

CO2Me

H

89% (3k)

CO2Me
Me
Me

CO2Me
73%h

CO2Me

2

60%h

(3n)
Me

CO2Me

(3o)

O
CO2Me

NH
O

H
O

CO2Me

R = Me, 90%, 82%f (3i)
R = CO2Me, 81% (3j)

R = SnBu3, 54%g (3l)
R = CN, 51% (3m)
O
H
H

a

CO2Me
OPiv

CO2Me

R

N

CO2Me
60% (3f)

S

R

R1 = Me; R2 = H; 75%d (3g)
R1 = H; R2 = Me; 68%e (3h)

R2
R2 =

N
L7

CO2Me

Me
R1

Me

CO2Me

CO2Me

R3

R3

N

CO2Me
3a-3q

CO2Me

4

8

N
R1

Ph

Ph

R = H, 74%, 73%c (3a)
R = CF3, 89% (3b)
R = F, 70% (3c)
R = i-Bu, 64% (3d)
R = OMe, 67% (3e)

R1

2a (%)b,c

1

R1

CO2Me

CO2Me

Table 1. Optimization of the Reaction Conditions.a
NiBr4(TBA)2 (5 mol%)
L7 (5 mol%)

Mn, CO2 (1 atm)
DMA, 50 ºC
then, TMSCHN2 &
B2(OH)4-H2O

R3

a,b

3

52%e (3p)

CO2Me
57%h (3q)

4

CO2Me

a

As Table 1 (entry 1), followed by exposure to
TMSCHN2 and Pd/C (5 mol%), B2(OH)4 (2 equiv) and
H2O (5 equiv) at rt. b Isolated yields, average of two
independent runs, using 1,3-dienes as E/Z mixtures. c
Using E-1a. d dr = 1.5:1. e dr = 1:1. f 1 mmol scale. g
Using H2 and Pd/C as reductant. h NiBr4(TBA)2 (10
mol%) and L7 (10 mol%).

Once we established the optimized reaction conditions,
we next studied the generality of our catalytic dicarboxylation of 1,3-dienes (Table 2).19 In situ protection of
the carboxylic acid function as the methyl ester and
reduction of the pending alkene was necessary to avoid
unnecessary purification issues of the resulting adipic
acid derivatives.20 As expected, a host of 1,3-dienes
substituted with either aliphatic (1n-1q) or aromatic
backbones (1a-1m) reacted equally well with the
NiBr4(TBA)2/L7 couple. Notably, the outcome of the
latter was found to be insensitive to whether electronrich or electron-poor arenes were employed, even in the

presence of ortho-substituents (1i-1k). The site-selective
incorporation of multiple CO2 motifs into 1,3-dienes was
accompanied by an excellent chemoselectivity, as esters
(3j, 3k), nitriles (3m), ketones (3p) or amides (3q) were
well-tolerated. Interestingly, the presence of an organometallic reagent does not interfere with productive formation of 3l, thus demonstrating the complementarity of
our technique with classical nucleophilic/electrophilic
regimes.21,22 Likewise, the reaction could be applied in
the presence of heterocyclic cores (3f). As illustrated by
the successful preparation of 3g and 3h, the reaction
could also be extended to disubstituted 1,3-dienes, albeit
with lower diastereoselectivities. Although C–O electrophiles are inherently predisposed to nickel-catalyzed C–
C bond-forming reactions,23 we found that 3k could be
obtained in 89% yield, leaving ample room for further
derivatization via cross-coupling technologies.

stereochemical course of the dicarboxylation event
as Table 1
CO2Me
(entry 1)
then
+
TMSCHN2
MeO2C
MeO2C
major
10
60% yield
trans-11
(91:9)
stoichiometric studies with Ni(0)(L7)n

CO2H
CO2H
4
butadiene

Ph

Ph
N
Me

Me
5
piperylene

7a
61% (7a:7a’ = 93:7)
Me

N
L7

NiBr4(TBA)2 (5 mol%)
L7 (5 mol%)
Mn, CO2 (1 atm)
DMA, 50 ºC
then, H2

Me
6
isoprene

CO2H
CO2H
8a
63% (8a:8a’ = 99:1)

Me

CO2H
CO2H

9a
65% (9a:9a’ = 77:23)

In light of these results, we wondered whether our protocol could be used for the valorization of butadiene,
isoprene or piperylene, compounds that are obtained in
bulk as byproducts of the steam cracking in the production of ethylene.24 As shown in Scheme 2, this turned out
to be the case, and 7a-9a were all obtained in good
yields from the corresponding 1,3-diene feedstocks after
a subsequent hydrogenolysis event. Strikingly, butadiene
4 resulted in a 93:7 regioselectivity pattern whereas the
presence of a methyl group in either 5 or 6 had a nonnegligible effect on site-selectivity, with 5 providing the
best regiochemical discrimination (8a).25 Although the
1,4–ratio of 7a and 9a could partially be improved by
using either L5 or L2 in lieu of L7, significant lower
yields were observed in these cases.15 Taken together,
the results summarized in Table 2 and Scheme 2 stand as
a testament to the potential of this catalytic technology
for enabling a site-selective incorporation of multiple
CO2 units into abundant 1,3-diene precursors.
Scheme 3. Mechanistic Experiments.

Ni

Ni-1 (1 equiv)
TBAB (1 equiv)

L7 (1 equiv)
TBAB (1 equiv)
Ni
Ni-2

Me

Ph

Ni-1

2a

Ph
Cy3P

N
N

N
Ph

Ph

Me

N

Mn (1 equiv), 50 ºC
0%
stoichiometric studies with Ni-2

Scheme 2. Ni-catalyzed Carboxylation of Diene Feedstocks.

minor
cis-12

Ph

Ni(COD)2 (1 equiv)
L7 (1 equiv)
TBAB (1 equiv)
Mn (1 equiv), 50 ºC
56% (E:Z = 69:31)
1a
+
CO2
(1 atm)

CO2Me

O
O

Mn (1 equiv), 50 ºC
CO2 (1 atm)
37% (E:Z = 36:64)

Ni-1

2a

Ni-2

Next, we decided to gather indirect evidence about the
mechanism by studying the stereochemical course of 10
with CO2 (Scheme 3, top). Interestingly, trans-11 was
preferentially formed over cis-12, suggesting that the
second CO2 unit is inserted into the p-allyl complex I
(Scheme 1) via formal backside attack.26 This seemingly
trivial interpretation, however, does certainly not rule
out a rapid interconversion of the putative p-allyl nickel
complexes upon exposure to Ni(0)(L7) prior to CO2
insertion.27 Although unraveling the mechanistic underpinnings of this reaction should await further investigations, we turned our attention to study the reactivity of
Ni-1 (Scheme 3, middle). This complex was easily prepared by exposure of L7 and Ni(COD)2 in benzene at 40
ºC, the structure of which was univocally determined by
X-ray crystallography.15 Interestingly, the reactivity of
Ni-1 with 1a was not comparable to that observed with
Ni(COD)2/L7, with not even traces of 2a being observed
in the former.28 While one might attribute this finding to
the non-innocent role of COD,29 the reluctance of
coordinatively saturated Ni-1 to dissociate L7 prior to
1,3-diene binding seems more likely. Unfortunately, the
preparation of p-allyl complex I (Scheme 1) in pure
analytical form bearing L7 as ligand proved to be particularly elusive. Gratifyingly, we could prepare structurally-related Ni-2, and the h3-hapticity of the allyl
motif was finally revealed by X-ray structure analysis
(bottom).15 Interestingly, we found that Ni-2 only furnished 2a in the presence of both L7 and Mn.15,30
Whether these results suggest that single-electron transfer processes come into play via putative Ni(I) species31
or invoke other mechanistic interpretations is the subject
of ongoing studies.

In summary, we have documented a site-selective, catalytic incorporation of multiple CO2 molecules into
abundant 1,3-dienes, thus giving access to adipic acids
from simple and available precursors. The salient features of this method are its excellent regio- and
chemoselectivity, mild conditions and ease of execution.
Further extensions to other hydrocarbons, including
asymmetric transformations, are currently in progress.

(6)

(7)

ASSOCIATED CONTENT
Supporting Information. Experimental procedures, crystallographic data and spectral data. This material is available free of charge via the Internet at http://pubs.acs.org.

(8)

AUTHOR INFORMATION
Corresponding Author

* rmartinromo@iciq.es

(9)

Funding Sources

No competing financial interests have been declared.

(10)

ACKNOWLEDGMENT
We thank ICIQ, MINECO (CTQ2015-65496-R & Severo
Ochoa Accreditation SEV-2013-0319) for support. A. T.
thanks MINECO for a FPU fellowship. We sincerely thank
M. Martínez, E. Escudero & E. Martin for X-ray crystallographic data and Dr. M. Gaydou for helpful discussions.

(11)

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For an isolated Ni-catalyzed 1,2-dicarboxylation of endcapped silyl allenes requiring excess amounts of DBU and
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Y.; Terao, J.; Sakaki, S.; Tsuji, Y. Org. Lett. 2014, 16, 4960.
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2016, 55, 5053. (d) Börjesson, M.; Moragas, T.; Martin, R.
J. Am. Chem. Soc. 2016, 138, 7504. (e) refs. 5b and 5d.
For seminal studies that required stoichiometric amounts of
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W. J. Organomet. Chem. 1984, 266, 313. (b) Behr, A.;
Kanne, U. J. Organomet. Chem. 1986, 317, 41. (c) Takimoto, M.; Mori, M. J. Am. Chem. Soc. 2001, 123, 2895.
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While this publication was under preparation, an elegant
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–W.; Liao, L. –L.; Ju, T.; Ye, J. –H.; Zhang, Z.; Li, J.; Yu,
D. –G. J. Am. Chem. Soc. 2017, 139, 17011.
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Al-Shihi, B.; Beller, M. ChemCatChem, 2017, 9, 542. (b)
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For details, see Supporting Information.
Ammonium salts have been reported to speed up the
reduction of nickel by Mn: (a) Iyoda, M.; Otsuka, H.; Sato,
K.; Nisato, N.; Oda, M. Bull. Chem. Soc. Jpn. 1990, 63, 80.
(b) Fujihara, T.; Nogi, K.; Xu, T.; Terao, J.; Tsuji, Y. J. Am.
Chem. Soc. 2012, 134, 9106.
For selected references in which ortho-substituents on the
nitrogen ligand exerted a critical influence on carboxylation
reactions, see: (a) ref. 7. (b) Nogi, K.; Fujihara, T.; Terao, J.;
Tsuji, Y. J. Org. Chem. 2015, 80, 11618.
The use of organic reductants or Me2Zn instead of Mn as
reducing agents led to no formation of 2a. See ref 15.
The mass balance accounts for unreacted starting material
and competitive polymerization of the 1,3-diene. Notably,
no reaction took place under CO2 pressure (10 bars).

(20) Regardless of whether aromatic or aliphatic dienes were
employed, Z:E selectivities ranging from 1.5:1 to 2.5:1 were
obtained. Competitive olefin isomerization was prevented
by conducting the hydrogenolysis with B2(OH)4-H2O:
Cummings, S. P.; Le, T.-N.; Fernandez, G. E.; Quiambao,
L. G.; Stokes, B. J. J. Am. Chem. Soc. 2016, 138, 6107.
(21) Metal-Catalyzed Cross-Coupling Reactions; Wiley-VCH
Verlag GmbH: Weinheim, Germany, 2008.
(22) Not even traces of benzoic acid from CO2 insertion into the
C–Sn bond were observed in the crude mixtures. For the
direct carboxylation of organometallic reagents: Correa, A.;
Martin, R. Angew. Chemie Int. Ed. 2009, 48, 6201.
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2015, 48, 886. (c) Rosen, B. M.; Quasdorf, K. W.; Wilson,
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Chem. Rev. 2011, 111, 1346.
(24) Weissermel, K.; Arpe, H. In Industrial Organic Chemistry;
Wiley-VCH Verlag GmbH: Weinheim, Germany, 2007;
105.

(25) Although tentative, these results can be interpreted on the
basis of a subtle influence on both steric and electronic
effects on the reactivity of p-allyl complex I (Scheme 1).
(26) This finding is in excellent agreement with conclusions
previously reached by Sato with stoichiometric amounts of
Ni complexes and pyrophoric reagents. See ref. 8c.
(27) Such interpretation was invoked by Jarvo in non-related
stereospecific Ni-catalyzed reactions. See: Yonova, I. M.;
Johnson, A. G.; Osborne, C. A.; Moore, C. E.; Morrissette,
N. S.; Jarvo, E. R. Angew. Chemie Int. Ed. 2014, 53, 2422.
(28) Control experiments revealed that the Ni(0)/L7 combination
isomerizes the Z isomer into the E isomer. No reaction or an
erosion in yield was observed when Ni-1 or Ni(COD)2/L7
were exposed to 1a without Mn. See ref 15.
(29) Nett, A. J.; Zhao, W.; Zimmerman, P. M.; Montgomery, J.
J. Am. Chem. Soc. 2015, 137, 7636.
(30) In the absence of L7, Mn or TBAB, low yields of
monocarboxylic acids were observed in the crude mixtures.
(31) Nickel (I) species have been reported to rapidly react with
CO2: Menges, F. S.; Craig, S. M.; Tötsch, N.; Bloomfield,
A.; Ghosh, S.; Krüger, H. J.; Johnson, M. A. Angew.
Chemie Int. Ed. 2016, 55, 1282. See ref 15 for control experiments with radical inhibitors.

Ni catalyst / Ligand
L
+
1,3-dienes

CO2

δ–

Ni

O

O

CO2H
CO2H

latent nucleophile
Site-selective incorporation of multiple CO2 motifs
Excellent chemo- & regioselectivity profile
Wide scope & mild conditions

22 examples
up to 90% yield