Communication
ChemComm
We thank Syngenta and the Engineering and Physical
Sciences Research Council (EPSRC) for iCASE funding for
LAH, ref. EP/H011455.
Conflicts of interest
There are no conflicts to declare.
Notes and references
1
For selected reviews concerning manganese catalysis in general, see:
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016, 3912–3929; (b) R. A. Baglia, J. P. T. Zaragoza and D. P.
(
2
Goldberg, Chem. Rev., 2017, 117, 13320–13352; (c) F. Kallmeier
and R. Kempe, Angew. Chem., Int. Ed., 2018, 57, 46–60;
(
d) M. Stanbury, J.-D. Compain and S. Chardon-Noblat, Coord. Chem.
Rev., 2018, 361, 120–137.
Scheme 2 (a) Effect of addition of EtCO
acetylene 6. (b) Effect of addition of EtCO
2
H to a reaction with diphenyl-
2
H to a reaction with 8.
2
3
4
M. I. Bruce, B. L. Goodall, M. Z. Iqbal, F. G. A. Stone, R. J. Doedens
and R. G. Little, J. Chem. Soc. D, 1971, 1595–1596.
B. Zhou, H. Chen and C. Wang, J. Am. Chem. Soc., 2013, 135,
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Selected examples: (a) R. He, Z.-T. Huang, Q.-Y. Zheng and C. Wang,
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L. Ackermann, Angew. Chem., Int. Ed., 2015, 54, 4092–4096;
We next turned our attention to the reaction with substrate
, which had previously allowed us to characterise a key
8
(
1
c) B. Zhou, Y. Hu and C. Wang, Angew. Chem., Int. Ed., 2015, 54,
3659–13663; (d) W. Liu, J. Bang, Y. Zhang and L. Ackermann,
7-membered manganacyclic intermediate, the anvil point to
6
subsequent protonation or reductive elimination, with the
latter being preferred under typical catalytic reaction conditions
Angew. Chem., Int. Ed., 2015, 54, 14137–14140; (e) C. Wang, A. Wang
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(
f ) Q. Lu, S. Cembellin, S. Greßies, S. Singha, C. G. Daniliuc and
(
Scheme 2b). Quite remarkably we discovered that the reaction
+ 4a - 9 was made feasible by the addition of propionic acid
affording 9 in 43% yield (isolated product after chromatography)
Scheme 2b). This result highlights the ability of acid additives to
F. Glorius, Angew. Chem., Int. Ed., 2018, 57, 1399–1403.
Y. Hu, B. Zhou and C. Wang, Acc. Chem. Res., 2018, 51, 816–827.
8
5
6 N. P. Yahaya, K. M. Appleby, M. Teh, C. Wagner, E. Troschke,
J. T. W. Bray, S. B. Duckett, L. A. Hammarback, J. S. Ward,
J. Milani, N. E. Pridmore, A. C. Whitwood, J. M. Lynam and
I. J. S. Fairlamb, Angew. Chem., Int. Ed., 2016, 55, 12455–12459.
7 L. A. Hammarback, I. P. Clark, I. V. Sazanovich, M. Towrie,
A. Robinson, F. Clarke, S. Meyer, I. J. S. Fairlamb and J. M. Lynam,
Nat. Catal., 2018, 1, 830–840.
(
promote the protonation pathway, with concomitant formation of
alkenylated products.
To summarise, we set out to understand the role of the
2 2
conjugate acid, [Cy NH ]X, formed by protonation of co-catalytic
8
L. A. Hammarback, A. Robinson, J. M. Lynam and I. J. S. Fairlamb,
J. Am. Chem. Soc., 2019, 141, 2316–2322.
H. Wang, F. Pesciaioli, J. C. A. Oliveira, S. Warratz and L. Ackermann,
Angew. Chem., Int. Ed., 2017, 56, 15063–15067.
I
Cy NH base, in influencing C–H bond activation catalysis at Mn .
2
9
We conclude that conjugate acids positively influence C–H bond
alkenylation catalysis involving terminal and internal alkynes,
which are found to be critical to productive catalysis. Importantly,
the promotional effect of acid did enable unreactive substrates to
be alkenylated involving both internal and terminal alkynes
1
1
1
0 L. Shi, X. Zhong, H. She, Z. Lei and F. Li, Chem. Commun., 2015, 51,
7136–7139.
1 B. Zhou, P. Ma, H. Chen and C. Wang, Chem. Commun., 2014, 50,
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2 For ‘Mn(OH)(CO)
Zaworotko, J. Chem. Soc., Chem. Commun., 1991, 1607–1608; For
Mn(SR)(CO)3’ type clusters, see: (b) S. Gl ¨a ser, R. Mede, H. G o¨ rls,
1
3
’ type clusters, see: (a) M. D. Clerk and M. J.
(Scheme 2). A dichotomy in behaviour is seen on switching from
‘
alkynes to an acrylate substrate, where catalysis is hindered by the
presence of the conjugate acid containing a halide anion (cf. not
S. Seupel, C. Bohlender, R. Wyrwa, S. Schirmer, S. Dochow,
G. U. Reddy, J. Popp, M. Westerhausen and A. Schiller, Dalton
2
a non-coordinating BF
4
anion). A secondary benefit of the
Trans., 2016, 45, 13222–13233; For ‘Ru(s,m -alkynyl)(CO)
3
’ type
I
clusters, see: (c) S. Bock, C. F. Mackenzie, B. W. Skelton,
L. T. Byrne, G. A. Koutsantonis and P. J. Low, J. Organomet. Chem.,
[
Cy NH ]X salts is to thwart Mn catalyst degradation to form
2
2
inactive manganese clusters, which is an issue requiring attention
2016, 812, 190–196.
8
in future catalyst design studies.
13 P. Y. Bruice, Organic Chemistry, 5th edn, Pearson, 2007.
Chem. Commun.
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