Α-Alkylation of Ketones with Secondary Alcohols Catalyzed by Well-Defined Cp*CoIII-Complexes

Article abstract of DOI:10.1002/cssc.201900990

Although α-alkylation of ketones with primary alcohols by transition-metal catalysis is well-known, the same process with secondary alcohols is arduous and complicated by self-condensation. Herein a well-defined, high-valence cobalt(III)-catalyst was applied for successful α-alkylation of ketones with secondary alcohols. A wide-variety of secondary alcohols, which include cyclic, acyclic, symmetrical, and unsymmetrical compounds, was employed as alkylating agents to produce β-alkyl aryl ketones.

Full text of DOI:10.1002/cssc.201900990

DOI: 10.1002/cssc.201900990
Communications
a-Alkylation of Ketones with Secondary Alcohols
Catalyzed by Well-Defined Cp*CoIII-Complexes
Priyanka Chakraborty,[a] Manoj Kumar Gangwar,[a] Balakumar Emayavaramban,[a]
Eric Manoury,[b] Rinaldo Poli,[b] and Basker Sundararaju*[a]
Although a-alkylation of ketones with primary alcohols by
transition-metal catalysis is well-known, the same process with
secondary alcohols is arduous and complicated by self-conden-
sation. Herein a well-defined, high-valence cobalt(III)-catalyst
was applied for successful a-alkylation of ketones with secon-
dary alcohols. A wide-variety of secondary alcohols, which in-
clude cyclic, acyclic, symmetrical, and unsymmetrical com-
pounds, was employed as alkylating agents to produce b-alkyl
aryl ketones.
Formation of CÀC bonds in organic synthesis generally in-
volves a multistep process entailing alkyl halides, organometal-
lic coupling partners, and other reducing agents, which gener-
ate copious amounts of waste.[1] Development of atom-eco-
nomical, environmentally friendly, and sustainable methods is
Scheme 1. Overview of a-alkylation of ketones.
more desirable than traditional alkylation reactions. In this con-
text, the concept of “hydrogen borrowing” or “hydrogen auto-
transfer process”[2] has been tremendously exploited over the
past decade. This process involves transition-metal-catalyzed
dehydrogenation of alcohols into carbonyl compounds, which
are subsequently subjected to condensation in situ with car-
bonucleophiles to yield a,b-unsaturated carbonyl compounds,
followed by hydrogenation to afford C-alkylated ketones as
the end products.[3] The use of alcohols as alkylating reagents
is preferred because of their cost, ready availability, and envi-
ronmental friendliness. The a-alkylation of ketones with pri-
mary alcohols has been well explored,[4] but there are only a
few reports documented for secondary alcohols as alkylating
agents under noble-metal catalysis (Scheme 1a).[5,6] Traditional-
ly, b-secondary alkylation of ketones has been achieved by
using strong bases (e.g., lithium diisopropylamide, nBuLi, etc.)
and secondary alkyl halides. The reaction naturally produces
large amounts of waste with appreciable selectivity.[7] a-Alkyla-
tion of carbonyl compounds by using primary alcohols has
been widely investigated with 3d transition metals
(Scheme 1b).[8,9] It is worth mentioning that dehydrogenation
of secondary alcohols is an uphill process. To the best of our
knowledge, no catalytic system based on base metals was pre-
viously reported for the a-alkylation of carbonyl compounds
with secondary alcohols.
It is worth mentioning that Donohoe and co-workers report-
ed the a-alkylation of ketones with secondary alcohols to form
b-branched products by using a Cp*IrIII dimer; they have also
addressed the issue of simultaneous self-condensation of the
carbonyl substrate and the ketone derived from the alcohol by
employing a sterically bulkier aryl ketone as the carbonyl sub-
strate.[5c,d] Inspired by these results and by our ongoing efforts
to design inexpensive and sustainable processes under high-
valence cobalt catalysis,[10] we recently reported a well-defined
Cp*CoIII complex for efficient dehydrogenation of secondary al-
cohols into the corresponding ketones and amines.[11] Based
on our earlier studies on dehydrogenation of secondary alco-
hols, we envisioned that the Cp*CoIII catalytic system could be
exploited for the a-alkylation of ketones with secondary alco-
hols to access b-alkyl ketones. We herein report our successful
results of a-alkylation of carbonyl compounds with secondary
alcohols by employing well-defined and high-valence Cp*-CoIII
as the catalyst (Scheme 1c).
[a] P. Chakraborty, Dr. M. K. Gangwar, B. Emayavaramban, Prof. B. Sundararaju
Department of Chemistry
Indian Institute of Technology Kanpur
Kanpur, Uttar Pradesh 208 016 (India)
E-mail: basker@iitk.ac.in
[b] Dr. E. Manoury, Prof. R. Poli
Fine CNRS, LCC (Laboratoire de Chimie de Coordination)
Universitꢀ de Toulouse, UPS, INPT
205 Route de Narbonne
We began our investigations with 2,3,4,5,6-pentamethyl ace-
tophenone (1a) and 1-phenylethanol (2a) as model reactants
and by employing 10 mol% of Cp*Co(CO)I2 as the catalyst in
the presence of tBuOK as the base in toluene (0.1m). The reac-
tion at 1508C for 24 h led to the expected a-alkylated produc-
F-31077 Toulouse Cedex 4 (France)
Supporting Information and the ORCID identification number(s) for the
author(s) of this article can be found under:
https://doi.org/10.1002/cssc.201900990.
ChemSusChem 2019, 12, 1 – 6
1
ꢀ 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
&
These are not the final page numbers! ÞÞ

Communications
Table 1. Reaction optimization.[a]
Entry
[Co] [mol%]
Ligand [mol%]
Yield[b] [%]
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
A (10)
B (10)
C (10)
A (10)
A (10)
A (10)
A (10)
A (10)
D (2)
D (2)
D (2)
D (2)
D (2)
–
–
–
44
55
38
32
59
n.r.
72
77
90
62[c]
73[d]
74[e]
74[f]
95[g]
16[h]
Scheme 2. Effect of substituents on arenes. d.r.=diastereomeric ratio.
PPh3(10)
PCy3 (10)
pyridine (10)
2-hydroxypyridine (10)
3da). Tetralone as the ketone source was also less effective
(3ea). However, the yields increased if the ortho-positions of
the aromatic ketone were methyl-substituted (3 fa, 3ga),
which highlights the necessity of crowding on the aromatic
ring to preclude substrate self-condensation.[4]
8-hydroxyquinoline (10)
–
–
–
–
–
–
To demonstrate the practical applicability of this system,
gram-scale reactions were tested for the synthesis of b-
branched C-alkylated products as shown in Scheme 3. Pleas-
ingly, the desired product 3aa formed in 93% yield with only
0.5 mol% of catalyst loading and 1-phenylethanol (2a) as the
alkylating agent. A gram-scale reaction conducted with 3-pen-
tanol also provided the expected product 3at in good yields
(Scheme 3). In this case, lowering the catalyst loading to 0.05%
led to 33% yield (0.45 g of product 3at), corresponding to a
turnover number (TON) of 2010.
D (2)
D (2)
[a] Standard reaction conditions: 1a (0.1 mmol), 2a (0.2 mmol), [Co]
(0.002–0.01 mmol), tBuOK (0.2 mmol) in toluene (0.1m), at 1508C for 24 h.
[b] Isolated yields. [c] tAmOH used as solvent. [d] Bu2O used as solvent.
[e] tBuONa used as base. [f] 1.5 equiv. of base used. [g] Conducted at 1m
concentration. [h] Performed at 1308C. n.r.=no reaction.
t 3aa in 44% isolated yield (Table 1, entry 1). Encouraged by
this result, we screened other Cp*Co complexes, only to ob-
serve a marginal improvement (38 and 55%, entries 2 and 3).
Addition of a phosphine ligand such as PPh3 or PCy3 to the
Cp*Co-monomer (A) yielded unsatisfactory results (32 and
59%, entries 4 and 5).
Further screening by employing s-donor ligands such as
pyridine also did not lead to any improvement in the product
formation (entry 6). However, to our delight, 2-hydroxypyridine
and 8-hydroxyquinoline led to remarkably better results, the
latter affording the product in 77% yield (entries 7 and 8). The
in situ-formed Cp*Co(N,O)I complex (D) was reported by us
earlier[11] for the acceptorless dehydrogenation of secondary al-
cohols. Hence, we pursued the screening by using the well-de-
fined cobalt catalyst D, but with a lower catalyst loading
(2 mol%). Gratifyingly, the expected b-alkylated product 3aa
was isolated in 90% yield (entry 9). Use of other solvents and
bases was found to be detrimental (entries 10–12). Incidentally,
the yield of 3aa dropped to 74% if the base loading was low-
ered from 2 to 1.5 equiv. (entry 13). The product formation im-
proved to 95% if the reaction was performed at 1m concentra-
tion (entry 14). In contrast, lowering the temperature to 1308C
gave only a 16% yield (entry 15).
Scheme 3. Gram-scale synthesis.
We then examined the scope of the alcohols, and a summa-
ry of the results is presented in Scheme 4. Various aromatic
secondary alcohols bearing electron-donating substituents
such as Me and OMe gave the corresponding C-alkylated prod-
ucts in good yields (3ab, 3ac). Aryl alkyl secondary alcohols
with electron-withdrawing moieties such as F, Cl, and Br afford
moderate-to-good yields of the products (3ad–3ag) with the
substituents remaining unaffected. Naphthyl- and p-methoxy-
phenyl methyl-substituted alcohols provided the correspond-
ing products in satisfactory yields (3ah, 3ai). Furthermore, if
the alcohol contained a p-(phenylethynyl) substituent, the de-
sired product was selectively obtained with the alkyne moiety
intact (3aj). Surprisingly, heteroatom-containing 2-, 3-, and 4-
pyridyl secondary alcohols were also effective in leading to the
With the optimized conditions at our disposal, we explored
the scope of various aryl ketones and the effect of steric hin-
drance on the reactivity (Scheme 2). Unsubstituted aryl methyl
ketones led to poor yields owing to self-condensation (3ba–
&
ChemSusChem 2019, 12, 1 – 6
www.chemsuschem.org
2
ꢀ 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ÝÝ These are not the final page numbers!

Communications
1a. The corresponding cholesterol derivative 3ax
was isolated in 43% yield.
The diverse applications of b-alkyl aryl ketone 3aa
into various carbonyl derivatives are shown in
Scheme 5. Product 3aa was first treated with Br2 to
remove the pentamethylphenyl group as aroyl bro-
mide, and the intermediate was subsequently
trapped by various nucleophiles.[5c] Addition of n-oc-
tanol yielded the corresponding ester 5 in 83% yield.
Replacement of the alcohol with amines as nucleo-
philes afforded the corresponding amides 4, 6, and 7
in good yields. Clearly, the sterically bulkier pentame-
thylphenyl group not only inhibited the self-conden-
sation but also facilitated the synthesis of diverse b-
alkylcarbonyl derivatives.
To gain mechanistic insights, preliminary control
experiments were performed (Scheme 6). Deuterium-
labelling experiments were performed with 1a and
alcohol 2a-D to validate the involvement of hydro-
gen-borrowing methodology. Under standard condi-
tions, the reaction yielded the product 3aa-D in 73%
yield, which exhibited 55–64% deuterium incorpora-
tion [Scheme 6(i)]. To further confirm our hypothesis,
chalcone 9, prepared by self-condensation of aceto-
phenone, was also employed under standard condi-
tions with 2a-D as transfer-hydrogenation reagent,
providing the expected H/D-scrambled product 3ba-
D with 16–31% deuterium exchange [Scheme 6(ii)].
These studies suggest that the transfer-hydrogena-
tion step is reversible. Chalcone 9 and alcohol 2a
also yielded the product 3ba under our catalytic
system, suggesting that the hydride source is derived
from alcohol for the reduction step [Scheme 6(iii)].
Next, chiral (S)-(À)-1-phenylethanol was used as a
coupling partner, leading to the formation of the
racemized product 3aa in 86% yield, suggesting that
the reaction proceeds through a dehydrogenation
pathway because the chirality will be lost after dehy-
drogenation to the ketone [Scheme 6(iv)]. Whereas
the reaction with 2a, performed under the optimized
conditions but without catalyst, produced 3aa in ap-
proximately 30% yield and the reaction with 3-penta-
nol (2s) did not proceed at all, using D as catalyst re-
sulted in 71% yield of 3at, as shown in Scheme 6.
In conclusion, we have demonstrated the use of a phos-
phine-free, bench-stable, and well-defined high-valence CoIII
catalyst for the a-alkylation of ketones with secondary alco-
hols. Steric crowding in the aryl moiety of aryl alkyl ketones
was found to be important for prevention of self-condensation
and to exemplify the synthetic utility and scope of the derived
b-alkyl aryl ketones. Preliminary control experiments have been
performed to demonstrate the involvement of the “hydrogen
borrowing” process. Further studies are currently pursued in
our laboratory for isolation of the CoÀH intermediate and ra-
tionalization of mechanistic pathways through DFT calcula-
tions.
Scheme 4. Scope of secondary alcohols. [a] Performed with 5 equiv. alcohol.
desired products without catalyst poisoning, and their corre-
sponding (pyridin-2-yl)butanone derivatives were obtained in
good yields (3ak–3am). Diphenylmethanol provided the corre-
sponding alkylated products in a good yield. We further evalu-
ated the reactivity of aliphatic alcohols under our conditions.
To our delight, various cyclic secondary alcohols were found to
afford the products in moderate-to-good yields (3ao–3as).
Finally, we investigated more challenging long-chain acyclic ali-
phatic alcohols. It was found that excess amount of alcohol
was necessary to achieve the desired products in respectable
yields (3at–3aw). The developed methodology was also ex-
tended to the late-stage functionalization of cholesterol with
ChemSusChem 2019, 12, 1 – 6
www.chemsuschem.org
3
ꢀ 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
&
These are not the final page numbers! ÞÞ

Communications
Conflict of interest
The authors declare no conflict of interest.
Keywords: alkylation · cobalt · ketones · secondary alcohols ·
a-alkylation
[1] C. S. Yeung, V. M. Dong, Chem. Rev. 2011, 111, 1215–1292.
[2] Selected reviews on Hydrogen borrowing or Hydrogen auto-transfer
processes, see: a) G. Guillena, D. J. Ramꢁn, M. Yus, Angew. Chem. Int. Ed.
2007, 46, 2358–2364; Angew. Chem. 2007, 119, 2410–2416;
b) M. H. S. A. Hamid, P. A. Slatford, J. M. J. Williams, Adv. Synth. Catal.
2007, 349, 1555–1575; c) T. D. Nixon, M. K. Whittlesey, J. M. J. Williams,
Dalton Trans. 2009, 753–762; d) A. J. A. Watson, J. M. J. Williams, Science
2010, 329, 635–636; e) G. Guillena, D. J. Ramꢁn, M. Yus, Chem. Rev.
2010, 110, 1611–1641; f) G. E. Dobereiner, R. H. Crabtree, Chem. Rev.
2010, 110, 681–703; g) R. Yamaguchi, K.-I. Fujita, M. Zhu, Heterocycles
2010, 81, 1093–1140; h) S. Bꢂhn, S. Imm, L. Neubert, M. Zhang, H. Neu-
mann, M. Beller, ChemCatChem 2011, 3, 1853–1864; i) T. D.
Obora, Y. Ishii, Synlett 2011, 30–51; j) S. Pan, T. Shibata, ACS
Catal. 2013, 3, 704–712; k) J. M. Ketcham, I. Shin, T. P. Mont-
gomery, M. J. Krische, Angew. Chem. Int. Ed. 2014, 53, 9142–
9150; Angew. Chem. 2014, 126, 9294–9302; l) A. Nandaku-
mar, S. P. Midya, V. G. Landge, E. Balaraman, Angew. Chem.
Int. Ed. 2015, 54, 11022–11034; Angew. Chem. 2015, 127,
11174–11186; m) Q. Yang, Q. Wang, Z. Yu, Chem. Soc. Rev.
2015, 44, 2305–2329; n) G. Chelucci, Coord. Chem. Rev.
2017, 331, 1–36; o) A. M. Faisca Phillips, A. J. L. Pombeiro,
M. N. Kopylovich, ChemCatChem 2017, 9, 217–246; p) A.
Corma, J. Navas, J. M. Sabater, Chem. Rev. 2018, 118, 1410–
1459.
Scheme 5. Diversification of 3aa. Reactions conditions: (a) (i) Br2 (2 equiv.),
CH2Cl2, À178C, 15 min; (ii) n-octanol (3 equiv.), RT, 20 h; 83% (after 2 steps).
(b) (i) Br2 (2 equiv.), CH2Cl2, À178C, 15 min; (ii) MeONHMe·HCl (2 equiv.), Et3N
(4 equiv.), RT, 20 h; 68%. (c) (i) Br2 (2 equiv.), CH2Cl2, À178C, 15 min; (ii) pyrro-
lidine (3 equiv.), RT, 20 h; 82%. (d) (i) Br2 (2 equiv.), CH2Cl2, À178C, 15 min;
(ii) NH2CH2COOCH3·HCl (2 equiv.), Et3N (4 equiv.), RT, 20 h; 90%.
[3] a) R. H. Crabtree, Chem. Rev. 2017, 117, 9228–9246; b) F.
Huang, Z. Liu, Z. Yu, Angew. Chem. Int. Ed. 2016, 55, 862–
875; Angew. Chem. 2016, 128, 872–885; c) Y. Obora, Top.
Curr. Chem. 2016, 374, 11; d) J. R. Khusnutdinova, D. Milstein,
Angew. Chem. Int. Ed. 2015, 54, 12236–12273; Angew. Chem.
2015, 127, 12406–12445; e) Y. Obora, ACS Catal. 2014, 4,
3972–3981; f) C. Gunanathan, D. Milstein, Chem. Rev. 2014,
114, 12024–12087; g) C. Gunanathan, D. Milstein, Science
2013, 341, 1229712; h) A. C. Marr, Catal. Sci. Technol. 2012,
2, 279–287.
[4] a) C. S. Cho, B. T. Kim, T.-J. Kim, S. C. J. Shim, J. Org. Chem.
2001, 66, 9020–9022; b) J. Zhang, G. Leitus, Y. Ben-David, D.
Milstein, J. Am. Chem. Soc. 2005, 127, 10840–10841; c) R.
Martꢃnez, D. J. Ramꢁn, M. Yus, Tetrahedron 2006, 62, 8988–
9001; d) C. Gunanathan, L. J. W. Shimon, D. Milstein, J. Am.
Chem. Soc. 2009, 131, 3146–3147; e) B. Gnanaprakasam, Y.
Ben-David, D. Milstein, Adv. Synth. Catal. 2010, 352, 3169–
3173; f) Y. Iuchi, Y. Obora, Y. Ishii, J. Am. Chem. Soc. 2010,
132, 2536–2537; g) M. L. Buil, M. A. Esteruelas, J. Herrero, S.
Izquierdo, I. M. Pastor, M. Yus, ACS Catal. 2013, 3, 2072–
2075; h) T. J. Kozlowski, R. J. Davis, ACS Catal. 2013, 3, 1588–
1600; i) F. Li, J. Ma, N. Wang, J. Org. Chem. 2014, 79, 10447–
10455; j) D. Shen, D. L. Poole, C. C. Shotton, A. F. Kornahrens,
M. P. Healy, T. J. Donohoe, Angew. Chem. Int. Ed. 2015, 54,
1642–1645; Angew. Chem. 2015, 127, 1662–1665; k) R.
Frost, C. B. Cheong, W. M. Akhtar, D. F. J. Caputo, N. G. Ste-
venson, T. J. Donohoe, J. Am. Chem. Soc. 2015, 137, 15664–
15667; l) H. Aitchison, R. L. Wingad, D. F. Wass, ACS Catal. 2016, 6,
7125–7132; m) Y. Xie, Y. Ben-David, L. J. W. Shimon, D. Milstein, J. Am.
Chem. Soc. 2016, 138, 9077–9080; n) B. C. Roy, S. Debnath, K. Chakra-
barti, B. Paul, M. Maji, S. Kundu, Org. Chem. Front. 2018, 5, 1008–1018;
o) S. Shee, B. Paul, D. Panja, B. C. Roy, K. Chakrabarti, K. Ganguli, A. Das,
G. K. Das, S. Kundu, Adv. Synth. Catal. 2017, 359, 3888–3893.
[5] a) S. Thiyagarajan, C. Gunanathan, ACS Catal. 2018, 8, 2473–2478; b) S.
Thiyagarajan, C. Gunanathan, ACS Catal. 2017, 7, 5483–5490; c) W. M.
Akhtar, C. B. Cheong, J. R. Frost, K. E. Christensen, N. G. Stevenson, T. J.
Donohoe, J. Am. Chem. Soc. 2017, 139, 2577–2580; d) W. M. Akhtar, R. J.
Scheme 6. Preliminary mechanistic investigations.
Acknowledgements
Financial Support provided by CEFIPRA (IF-5805-1) to carry out
this work is gratefully acknowledged. P.C. and B.E. thank IITK for
their fellowship. M.K.G. thanks SERB for national post-doctoral
fellowship. PK Kelkar Young Faculty Award to B.S. is gratefully ac-
knowledged.
&
ChemSusChem 2019, 12, 1 – 6
www.chemsuschem.org
4
ꢀ 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ÝÝ These are not the final page numbers!

Communications
Armstrong, J. R. Frost, N. G. Stevenson, T. J. Donohoe, J. Am. Chem. Soc.
2018, 140, 11916–11920.
[6] During the preparation of this manuscript, Thiyagarajan and Gunana-
than reported Ru-catalyzed cross-coupling of secondary alcohols, see:
S. Thiyagarajan, C. Gunanathan, J. Am. Chem. Soc. 2019, 141, 3822–
3827.
19, 1080–1083; e) F. Freitag, T. Irrgang, R. Kempe, Chem. Eur. J. 2017,
23, 12110–12113; f) T. Liu, L. Wang, K. Wu, Z. Yu, ACS Catal. 2018, 8,
7201–7207; g) N. V. Kulkarni, W. W. Brennnessel, W. D. Jones, ACS Catal.
2018, 8, 997–1002; h) K. Polidano, B. D. W. Allen, J. M. J. Williams, L. C.
Morrill, ACS Catal. 2018, 8, 6440–6445; i) J. Das, K. Singh, M. Vellakkaran,
D. Banerjee, Org. Lett. 2018, 20, 5587–5591; j) K. Shimura, K. Kon,
S. M. A. H. Siddiki, K.-I. Shimizu, Appl. Catal. A 2013, 462–463, 137–142;
k) J. Das, M. Vellakaran, D. Banerjee, J. Org. Chem. 2019, 84, 769–779.
[10] a) R. Mandal, B. Sundararaju, Org. Lett. 2017, 19, 2544–2547; b) M. Sen,
P. Dahiya, R. Premkumar, B. Sundararaju, Org. Lett. 2017, 19, 3699–
3702; c) M. Sen, R. Mandal, A. Das, D. Kalsi, B. Sundararaju, Chem. Eur. J.
2017, 23, 17454–17457; d) M. Sen, N. Rajesh, B. Emayavaramban, J. R.
Premkumar, B. Sundararaju, Chem. Eur. J. 2018, 24, 342–346; e) R.
Mandal, B. Emayavaramban, B. Sundararaju, Org. Lett. 2018, 20, 2835–
2838; f) D. Kalsi, S. Dutta, N. Barsu, M. Rueping, B. Sundararaju, ACS
Catal. 2018, 8, 8115–8120; g) B. Emayavaramban, P. Chakraborty, B.
Sundararaju, ChemSusChem 2018, DOI: https://doi.org/10.1002/
cssc.201802144; also see h) T. Yoshino, S. Matsunaga, Adv. Synth. Catal.
2017, 359, 1245–1262.
[7] a) M. T. Reetz, Angew. Chem. Int. Ed. Engl. 1982, 21, 96–108; Angew.
Chem. 1982, 94, 97–109; b) D. Caine, Comprehensive Organic Synthesis,
Vol. 3 (Eds.: B. M. Trost, I. Fleming), Pergamon, Oxford, 1991, pp. 1–63.
[8] a) A. Quintard, J. A. Rodriguez, ChemSusChem 2016, 9, 28–30; b) B. Maji,
M. K. Barman, Synthesis 2017, 49, 3377–3393; c) M. Garbe, K. Junge, M.
Beller, Eur. J. Org. Chem. 2017, 4344–4362; d) E. Balaraman, A. Nandaku-
mar, G. Jaiswal, M. K. Sahoo, Catal. Sci. Technol. 2017, 7, 3177–3195;
e) G. A. Filonenko, R. Van Putten, E. J. M. Hensen, E. A. Pidko, Chem. Soc.
Rev. 2018, 47, 1459–1483; f) Y. Cai, F. Li, Y.-Q. Li, W.-B. Zhang, F.-H. Liu,
S.-L. Shi, Tetrahedron Lett. 2018, 59, 1073–1079; g) F. Kallmeier, R.
Kempe, Angew. Chem. Int. Ed. 2018, 57, 46–60; Angew. Chem. 2018,
130, 48–63; h) B. G. Reed-Berendt, K. Polidano, L. C. Morill, Org. Biomol.
Chem. 2019, 17, 1595–1607; i) T. Irrgang, R. Kempe, Chem. Rev. 2019,
119, 2524–2549; j) L. Alig, M. Fritz, S. Schneider, Chem. Rev. 2019, 119,
2681–2751.
[9] a) S. Elangovan, J.-B. Sortais, M. Beller, C. Darcel, Angew. Chem. Int. Ed.
2015, 54, 14483–14486; Angew. Chem. 2015, 127, 14691–14694; b) M.
Pen¼-Lꢁpez, P. Piehl, S. Elangovan, H. Neumann, M. Beller, Angew. Chem.
Int. Ed. 2016, 55, 14967–14971; Angew. Chem. 2016, 128, 15191–15195;
c) N. Deibl, R. Kempe, J. Am. Chem. Soc. 2016, 138, 10786–10789; S. Fu,
Z. Shao, Y. Wang, Q. Liu, J. Am. Chem. Soc. 2017, 139, 11941–11948;
d) G. Zhang, J. Wu, H. Zeng, S. Zhang, Z. Yin, S. Zheng, Org. Lett. 2017,
[11] a) M. K. Gangwar, P. Dahiya, B. Emayavaramban, B. Sundararaju, Chem.
Asian J. 2018, 13, 2445–2448; b) B. Emayavaramban, P. Chakraborty, E.
Manoury, R. Poli, B. Sundararaju, Org. Chem. Front. 2019, 6, 852–857.
Manuscript received: April 11, 2019
Revised manuscript received: June 10, 2019
Version of record online: && &&, 0000
ChemSusChem 2019, 12, 1 – 6
www.chemsuschem.org
5
ꢀ 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
&
These are not the final page numbers! ÞÞ

COMMUNICATIONS
P. Chakraborty, M. K. Gangwar,
B. Emayavaramban, E. Manoury, R. Poli,
B. Sundararaju*
&& – &&
a-Alkylation of Ketones with
Secondary Alcohols Catalyzed by Well-
Defined Cp*CoIII-Complexes
Secondary success: A well-defined, air-
stable, CoIII-catalyzed a-alkylation of ke-
tones is achieved by using secondary al-
cohols as alkylating agents. A wide-vari-
ety of secondary alcohols, which include
cyclic, acyclic, symmetrical, and unsym-
metrical compounds, is employed as al-
kylating agents to produce b-alkyl aryl
ketones.
&
ChemSusChem 2019, 12, 1 – 6
www.chemsuschem.org
6
ꢀ 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ÝÝ These are not the final page numbers!