Catalytic Oxo/Imido Heterometathesis by a Well-Defined Silica-Supported Titanium Imido Complex

Article abstract of DOI:10.1002/anie.201804346

Grafting Ti(=NtBu)(Me₂Pyr)₂(py)₂ (Me₂Pyr= 2,5-dimethylpyrrolyl, py=pyridine) onto the surface of silica partially dehydroxylated at 700 °C gives the well-defined silica-supported Ti imido complex (≡SiO)Ti(=NtBu)(Me₂Pyr)(py)₂, which is fully characterized by IR and solid-state NMR spectroscopy as well as elemental and mass balance analyses. While stoichiometric imido-transfer reactivity is typical for Ti imides, the obtained surface complex is unique in that it enables catalytic transformations involving Ti imido and oxo intermediates. In particular, it efficiently catalyzes imidation of carbonyl compounds with N-sulfinylamines by oxo/imido heterometathesis.

Full text of DOI:10.1002/anie.201804346

A Journal of the Gesellschaft Deutscher Chemiker
Angewandte
Chemie
International Edition
www.angewandte.org
Accepted Article
Title: Catalytic Oxo/Imido Heterometathesis by a Well-Defined Silica-
Supported Titanium Imido Complex
Authors: Pavel A. Zhizhko, Andrey V. Pichugov, Nikolai S. Bushkov,
Florian Allouche, Anton A. Zhizhin, Dmitry N. Zarubin, and
Nikolai A. Ustynyuk
This manuscript has been accepted after peer review and appears as an
Accepted Article online prior to editing, proofing, and formal publication
of the final Version of Record (VoR). This work is currently citable by
using the Digital Object Identifier (DOI) given below. The VoR will be
published online in Early View as soon as possible and may be different
to this Accepted Article as a result of editing. Readers should obtain
the VoR from the journal website shown below when it is published
to ensure accuracy of information. The authors are responsible for the
content of this Accepted Article.
To be cited as: Angew. Chem. Int. Ed. 10.1002/anie.201804346
Angew. Chem. 10.1002/ange.201804346
Link to VoR: http://dx.doi.org/10.1002/anie.201804346
http://dx.doi.org/10.1002/ange.201804346

10.1002/anie.201804346
Angewandte Chemie International Edition
COMMUNICATION
Catalytic Oxo/Imido Heterometathesis by a Well-Defined Silica-
Supported Titanium Imido Complex
Pavel A. Zhizhko,*[a] Andrey V. Pichugov,[a],[b] Nikolai S. Bushkov,[a],[c] Florian Allouche,[d] Anton A.
Zhizhin,[a] Dmitry N. Zarubin,*[a] and Nikolai A. Ustynyuk[a]
Abstract:
Grafting
Ti(=NtBu)(Me2Pyr)2(py)2
(Me2Pyr
=
to the low stability of the most reactive imido or the
corresponding oxo complexes.
2,5-dimethylpyrrolyl, py = pyridine) onto the surface of silica partially
dehydroxylated at 700 °C gives a well-defined silica-supported Ti
imido complex (≡SiO)Ti(=NtBu)(Me2Pyr)(py)2 fully characterized by
IR, solid-state NMR, elemental and mass balance analyses. While
stoichiometric imido-transfer reactivity is typical for Ti imides, the
obtained surface complex is unique in that it enables catalytic
transformations involving Ti imido and oxo intermediates. In
particular, it efficiently catalyzes imidation of carbonyl compounds
with N-sulfinylamines via oxo/imido heterometathesis.
We have previously shown that readily accessible
N-sulfinylamines (RN=S=O), that are efficient imidating agents
for oxo complexes,[7] can be used to complete the oxo/imido
heterometathesis catalytic cycle (Scheme 1).[8] Our initial
attempts focused on Mo and V,[8a-8d] and more recently Ta.[8e]
However, the reactivity of the imido complexes increases
drastically when going left across the d-block of the Periodic
Table,[9] the most exciting examples being found for Ti[1c, 5a-5f]
and Zr[1b, 5g-5i] by Mountford, Bergman, and others. At the same
time, terminal oxo derivatives of these metals show
a
Among various reactivity patterns of metal–ligand multiply
bonded fragments,[1] metathesis reactions (i.e. those proceeding
via a cycloaddition/cycloreversion pathway) constitute one of the
most useful and mechanistically intriguing classes. While study
of the alkylidene complexes has led to the development of the
efficient olefin metathesis methodology,[2] catalytic metathesis of
multiple bonds between heteroatoms (heterometathesis)
remains much less developed. We have been particularly
attracted by the synthetic potential of the heterometathetical
imido-transfer reactions intrinsic to transition metal imido
complexes. Imido/imido heterometathesis (e.g. metathesis of
imines[3] or carbodiimides[4]) has been extensively studied
mechanistically, though has limited practical utility. On the other
hand, numerous examples of stoichiometric reactions of imido
complexes with various oxo compounds (organic carbonyl and
carboxyl derivatives, isocyanates, nitro and nitroso compounds,
CO2, etc.) show that almost any X=O bond can in principle be
transformed into the corresponding imino derivative (X=NR) via
oxo/imido heterometathesis.[1b, 1c, 5] However only a few metal-
catalyzed reactions of this type are reported to date,[5n, 6] in part
because of the lack of a convenient imido source, but also due
pronounced tendency to oligomerization with the formation of
bridging μ-oxo ligands, which restricts their application in
catalysis. We show here that this issue can be circumvented by
using Surface Organometallic Chemistry[10] to covalently attach
the metal site to the surface of the support and thus prevent the
oligomerization of the oxo intermediate. Ti imido species on the
surface of silica were previously only proposed to form in situ
during thermal decomposition of the corresponding supported
amides.[11] We report here preparation and full characterization
of
a
well-defined silica-supported Ti imido complex
(≡SiO)Ti(=NtBu)(Me2Pyr)(py)2 and present its activity in catalytic
oxo/imido heterometathesis that significantly surpasses the
activities of other systems developed to date.
[a]
Dr. P. A. Zhizhko, A. V. Pichugov, N. S. Bushkov, A. A. Zhizhin,
Dr. D. N. Zarubin, Prof. Dr. N. A. Ustynyuk
Laboratory for Organometallic Compounds
A. N. Nesmeyanov Institute of Organoelement Compounds, Russian
Academy of Sciences
Vavilov str., 28, 119991 Moscow (Russia)
E-mail: zhizhko@ineos.ac.ru
Scheme 1. Oxo/imido heterometathesis catalytic cycle.
E-mail: zaroubine@ineos.ac.ru
[b]
[c]
[d]
A. V. Pichugov
Higher Chemical College
D. Mendeleev University of Chemical Technology of Russia
Miusskaya sq., 9, 125047 Moscow (Russia)
N. S. Bushkov
Chemistry Department
Moscow State University
Vorob’evy Gory, 1, 119992 Moscow (Russia)
Dr. F. Allouche
Department of Chemistry and Applied Biosciences
ETH Zürich
Scheme 2. Synthesis and grafting of Ti(=NtBu)(Me2Pyr)2(py)2.
Vladimir-Prelog Weg, 1–5, CH-8093 Zürich (Switzerland)
Synthesis of the molecular precursor. An optimal molecular
precursor for a supported oxo/imido heterometathesis catalyst
Supporting information for this article is given via a link at the end of
the document.
This article is protected by copyright. All rights reserved.

10.1002/anie.201804346
Angewandte Chemie International Edition
COMMUNICATION
should contain the ligands that would render the imido ligand
terminal without creating a significant steric bulk, but also easily
cleavable by protonolysis with the surface hydroxyl groups of the
support. Me2Pyr ligand, widely used in Schrock-type imido-
alkylidene metathesis catalysts,[12] has the advantages of
adaptable sterics (via variable hapticity) and a propensity to
undergo clean protonolysis, which was utilized for instance in
preparation of MAP[12] and silica-supported catalysts.[13]
Ti(=NtBu)(Me2Pyr)2(py)2 was obtained as orange crystals by
treating Ti(=NtBu)Cl2(py)3 with 2 equiv of LiMe2Pyr in THF
(Scheme 2). Single-crystal X-ray diffraction reveals a monomeric
complex (Figure 1) containing terminal nearly linear imido ligand
(∠Ti–N–C 177.5(9)°, dTi=N 1.695(2) Å). The geometry at the
metal center can be described as distorted trigonal bipyramid
with 2 pyridines in apical positions, and imido and pyrrolyl
ligands in equatorial plane. Both pyrrolyls are 1 and their
rotation around Ti–N bonds is hindered as evidenced by the
presence of 2 resonances for the methyl groups of Me2Pyr in 1H
and 13C NMR (see ESI).
and imido (~30 ppm) ligands, as well as CH resonances of
pyrrolyl (~105 ppm) and pyridine (at ca. 124, 134, and 151 ppm)
ligands. Importantly, the signal of the quaternary carbon of
tert-butylimido group appears at ~70 ppm, indicating that imido
ligand stays intact during grafting. Noteworthy, no signals are
observed in 40–60 ppm region where the protonated imido
ligand would be observed. Overall, all the resonances observed
in the solid-state spectrum of Ti/SiO2 correspond to those found
in the liquid-state spectrum of the molecular precursor (see
Table 1 and Figure S4) in agreement with the proposed
structure of the surface complex (Scheme 2).
Figure 2. 13C CP MAS NMR spectrum of Ti/SiO2.
Table 1. 13C chemical shifts (/ppm) of Ti/SiO2 and Ti(=NtBu)(Me2Pyr)2(py)2.
Figure 1. Thermal ellipsoid plot of Ti(=NtBu)(Me2Pyr)2(py)2 at 50% probability
level. Hydrogen atoms are omitted for clarity. Atoms designated with prime (‘)
are related to their counterparts by the symmetry operator 1−X, +Y, 3/2−Z.
Selected bond distances (Å) and angles (deg): Ti1−N1 = 1.695(2), Ti1−N2 =
2.0964(12), Ti1−N3 = 2.2254(12), Ti1–N1–C1 = 177.5(9), N2–Ti1–N2’ =
134.69(7), N3–Ti1–N3’ = 167.15(6), N1–Ti1–N2 = 115.9(4), N1–Ti1–N3 =
93.0(3), N2–Ti1–N3 = 86.70(4).
[a]
Ti/SiO2
16.2
Ti(=NtBu)(Me2Pyr)2(py)2
Assignment
Me2Pyr
NCMe3
NCMe3
Me2Pyr
m-py
17.2 and 20.6
32.1
29.9
70.2
73.6
105.4
123.9
133.9
151.3
107.7 and 108.7
123.9
Preparation
of
the
supported
catalyst.
Grafting
Ti(=NtBu)(Me2Pyr)2(py)2 onto the surface of silica partially
dehydroxylated at 700 °C (SiO2-700) gives a bright yellow powder
Ti/SiO2 containing 1.0–1.2 wt% Ti (0.21–0.25 mmol Ti g−1). 1H
NMR of washings shows quantitative release of ca. 1.0 equiv of
Me2PyrH per Ti atom indicating the formation of a surface
138.1
p-py
151.8
o-py
complex
with
the
proposed
structure
[a] C6D6.
(≡SiO)Ti(=NtBu)(Me2Pyr)(py)2 (Scheme 2). Elemental analysis of
the solid shows Ti/N/C/H ratio of 1/3.9/19.1/33.9 close to the
expected value of 1/4/20/27. The consumption of surface
silanols during grafting is confirmed with IR spectroscopy (the
decrease of the corresponding band at 3747 cm−1; Figure S1).
Additionally, the CH and CH vibrations of the ligands appear in
the 3100–2800 cm−1 and 1600–1350 cm−1 regions.
Solid-state NMR gives further insight into the structure of the
surface complex. 13C CP MAS spectrum of Ti/SiO2 (Figure 2)
shows distinct peaks of methyl groups of pyrrolyl (at ~16 ppm)
Catalytic oxo/imido heterometathesis. To evaluate the
performance of Ti/SiO2 as an oxo/imido heterometathesis
catalyst we have tested it in a particular realization of the
general mechanism shown in Scheme 1—the imidation of
ketones with N-sulfinylamines that had been established before
with other metals.[8] The reaction between benzophenone and
N-sulfinyl-p-toluidine in boiling heptane (98 °C) at 1 mol%
This article is protected by copyright. All rights reserved.

10.1002/anie.201804346
Angewandte Chemie International Edition
COMMUNICATION
catalyst loading (Scheme 3) was used as a standard test to
compare Ti/SiO2 with the previously reported systems. The
results shown in Table 2 and Figure 3 demonstrate that Ti/SiO2
significantly outperforms all the catalysts developed so far. In
particular, V and Mo catalysts, that are very efficient in imidation
of aldehydes,[8c, 8d] display poor activities already in the case of
benzophenone, and only Ta[8e] is competent under these
conditions, albeit with much lower activity than Ti/SiO2. These
observations are fully consistent with the periodic trends
identified in the studies of stoichiometric reactivity of molecular
imido complexes and indicate that Ti is indeed the metal of
chose for these reactions.[1a-1c, 5, 9]
Figure 3. Catalytic performance of Ti/SiO2 and other oxo/imido
heterometathesis catalysts. The reaction is shown in Scheme 3; lines are
added to guide an eye.
Scheme 3. Oxo/imido heterometathesis between benzophenone and
N-sulfinyl-p-toluidine.
Table 3. Catalytic synthesis of ketimines using Ti/SiO2.
#
1
Product
mol% Ti[a]
Time
Yield[b]
85%
Table 2. Comparison of the activity of Ti/SiO2 and other benchmark oxo/imido
heterometathesis catalysts.[a]
1%
30 min
[b]
Catalyst
t
TOF15 min
385 (18)
116 (10)
9 (5)
,
[c] h−1
½
(≡SiO)Ti(=NtBu)(Me2Pyr)(py)2
(≡SiO)2Ta(=NtBu)(CH2CMe2Ph)[d]
(≡SiO)Mo(=NMes)2(CH2CMe2Ph)[e]
5 min
30 min
4 h
2
3
1%
1%
30 min
79%
70%
[f]
(≡SiO)V(=O)Cl2
~ 12 h
7 (5)
1 h
[a] The reaction is shown in Scheme 3. [b] Half-conversion time. [c] TOF
averaged for the first 15 min of the reaction; SD given in parentheses. [d]
[8e]
Ta(=NtBu)(CH2CMe2Ph)3/SiO2-300
.
[e] Catalyst prepared by grafting
Mo(=NMes)2(CH2CMe2Ph)2 onto SiO2-700 analogously to ref.[8d] [f]
[8c]
VOCl3/SiO2-500
.
4
5
1%
1%
30 min
75%
76%
To explore the scope of ketone imidation with N-sulfinylamines
catalyzed by Ti/SiO2 we have investigated the syntheses of
several ketimines focusing on the more challenging substrates
based on poorly nucleophilic anilines and bulky, heterocyclic, or
acid-sensitive (e.g. containing furan ring) ketones (Table 3).
Noteworthy, high activity of Ti/SiO2 allowed decreasing the
catalyst loading to 1 mol% in many cases, while Ta catalyst (the
most active among previously reported) typically required at
least 5 mol% to reach quantitative conversions.[8e] The results
summarized in Table 3 show that Ti-based catalytic oxo/imido
heterometathesis opens the way to facile and efficient water-free
synthesis of ketimines that are often difficult to access via
classical acid-catalyzed condensation of anilines and ketones.
2 h
6
7
2%
5%
30 min
1.5 h
88%
75%
[a] Based on total Ti content determined from elemental analysis. [b] Isolated
yield (quantitative conversions are observed in all cases, the yields are only
limited by losses during isolation, crystallization, and in some cases likely
adsorption on the catalyst).
For instance, the imine derivatives of diacetylferrocene (2[14a]
)
and diacetylpyridine (7[14b]) have been prepared previously via
tedious multi-day procedures and only in moderate yields.
In summary, we have applied the Surface Organometallic
Chemistry approach in combination with the findings from the
molecular organometallic chemistry on the stoichiometric
reactivity of the imido complexes to design a highly active
This article is protected by copyright. All rights reserved.

10.1002/anie.201804346
Angewandte Chemie International Edition
COMMUNICATION
Bernskoetter, P. J. Chirik, Organometallics 2004, 23, 3448; f) J. L.
Thorman, L. K. Woo, Inorg. Chem. 2000, 39, 1301; g) S. A. Blum, R. G.
Bergman, Organometallics 2004, 23, 4003; h) S. Y. Lee, R. G.
Bergman, J. Am. Chem. Soc. 1996, 118, 6396; i) J. L. Thorman, I. A.
Guzei, J. V. G. Young, L. K. Woo, Inorg. Chem. 2000, 39, 2344; j) P.
Royo, J. Sánchez-Nieves, J. Organomet. Chem. 2000, 597, 61; k) S. M.
Rocklage, R. R. Schrock, J. Am. Chem. Soc. 1980, 102, 7808; l) B.
Moubaraki, K. S. Murray, P. J. Nichols, S. Thomson, B. O. West,
Polyhedron 1994, 13, 485; m) M. Jolly, J. P. Mitchell, V. C. Gibson, J.
Chem. Soc., Dalton Trans. 1992, 1329; n) W.-D. Wang, J. H. Espenson,
Organometallics 1999, 18, 5170.
heterogeneous oxo/imido heterometathesis catalyst based on a
fully characterized well-defined silica-supported Ti imido
complex. This catalyst outperforms all the other previously
reported Mo, V, and Ta systems, as demonstrated for the
synthesis of imines. Further studies of the catalytic
transformations mediated by the supported group 4 transition
metal imido complexes are on the way in our laboratories.
Acknowledgements
[6]
a) K. R. Birdwhistell, T. Boucher, M. Ensminger, S. Harris, M. Johnson,
S. Toporek, Organometallics 1993, 12, 1023; b) S. L. Jain, V. B.
Sharma, B. Sain, J. Mol. Catal. A: Chem. 2005, 239, 92; c) W. Darwish,
E. Seikel, R. Käsmarker, K. Harms, J. Sundermeyer, Dalton Trans.
2011, 40, 1787.
This work was partially supported by Russian Foundation for
Basic Research (grant 16-33-00382) and by ETH Zürich. PZ
thanks Prof. Christophe Copéret for fruitful discussions and for
short stays at ETH Zürich, during which some part of this work
was done. PZ thanks Dr. René Verel for assistance with solid-
state NMR measurements.
[7]
[8]
K. A. Rufanov, J. Kipke, J. Sundermeyer, Dalton Trans. 2011, 40, 1990.
a) A. A. Zhizhin, D. N. Zarubin, N. A. Ustynyuk, Tetrahedron Lett. 2008,
49, 699; b) A. A. Zhizhin, D. N. Zarubin, N. A. Ustynyuk, Mendeleev
Commun. 2009, 19, 165; c) P. A. Zhizhko, A. A. Zhizhin, D. N. Zarubin,
N. A. Ustynyuk, D. A. Lemenovskii, B. N. Shelimov, L. M. Kustov, O. P.
Tkachenko, G. A. Kirakosyan, J. Catal. 2011, 283, 108; d) P. A.
Zhizhko, A. A. Zhizhin, D. N. Zarubin, N. A. Ustynyuk, Mendeleev
Commun. 2012, 22, 64; e) P. A. Zhizhko, A. A. Zhizhin, O. A.
Belyakova, Y. V. Zubavichus, Y. G. Kolyagin, D. N. Zarubin, N. A.
Ustynyuk, Organometallics 2013, 32, 3611.
Keywords: heterometathesis, imido, multiple bonds, supported
catalysts, titanium
[1]
a) W. A. Nugent, J. M. Mayer, Metal–Ligand Multiple Bonds, Wiley,
New York, 1988; b) A. P. Duncan, R. G. Bergman, Chem. Rec. 2002, 2,
431; c) N. Hazari, P. Mountford, Acc. Chem. Res. 2005, 38, 839; d) A. L.
Odom, Dalton Trans. 2005, 225; e) D. J. Mindiola, Acc. Chem. Res.
2006, 39, 813; f) D. J. Mindiola, Comments Inorg. Chem. 2008, 29, 73;
g) A. L. Odom, Dalton Trans. 2011, 40, 2689; h) M. T. Whited, Beilstein
J. Org. Chem. 2012, 8, 1554; i) T. L. Gianetti, H. S. La Pierre, J. Arnold,
Eur. J. Inorg. Chem. 2013, 3771; j) J. R. Webb, S. A. Burgess, T. R.
Cundari, T. B. Gunnoe, Dalton Trans. 2013, 42, 16646; k) A. L. Odom,
T. J. McDaniel, Acc. Chem. Res. 2015, 48, 2822; l) P. T. Wolczanski,
Organometallics 2018, 37, 505.
[9]
W. A. Nugent, R. J. McKinney, R. V. Kasowski, F. A. Van-Catledge,
Inorg. Chim. Acta 1982, 65, L91.
[10] a) C. Copéret, A. Comas-Vives, M. P. Conley, D. P. Estes, A. Fedorov,
V. Mougel, H. Nagae, F. Núñez-Zarur, P. A. Zhizhko, Chem. Rev. 2016,
116, 323; b) C. Copéret, F. Allouche, K. W. Chan, M. P. Conley, M. F.
Delley, A. Fedorov, I. B. Moroz, V. Mougel, M. Pucino, K. Searles, K.
Yamamoto, P. A. Zhizhko, Angew. Chem. Int. Ed. 2018, 57, 6398; c) J.
D. A. Pelletier, J.-M. Basset, Acc. Chem. Res. 2016, 49, 664; d) T. J.
Marks, Acc. Chem. Res. 1992, 25, 57; e) S. L. Wegener, T. J. Marks, P.
C. Stair, Acc. Chem. Res. 2012, 45, 206; f) R. Anwander, Chem. Mater.
2001, 13, 4419; g) Y. Liang, R. Anwander, Dalton Trans. 2013, 42,
12521.
[2]
[3]
a) R. R. Schrock, Angew. Chem. Int. Ed. 2006, 45, 3748; b) R. H.
Grubbs, Angew. Chem. Int. Ed. 2006, 45, 3760; c) Handbook of
Metathesis, 2nd ed. (Eds.: R. H. Grubbs, A. G. Wenzel, D. J. O'Leary, E.
Khosravi), Wiley, 2015.
[11] M. Beaudoin, S. L. Scott, Organometallics 2001, 20, 237.
[12] a) R. R. Schrock, Chem. Rev. 2009, 109, 3211; b) A. J. Jiang, J. H.
Simpson, P. Muller, R. R. Schrock, J. Am. Chem. Soc. 2009, 131,
7770; c) S. C. Marinescu, R. R. Schrock, P. Muller, A. H. Hoveyda, J.
Am. Chem. Soc. 2009, 131, 10840; d) R. R. Schrock, A. J. Jiang, S. C.
Marinescu, J. H. Simpson, P. Muller, Organometallics 2010, 29, 5241.
[13] a) F. Blanc, R. Berthoud, A. Salameh, J. M. Basset, C. Copéret, R.
Singh, R. R. Schrock, J. Am. Chem. Soc. 2007, 129, 8434; b) V.
Mougel, C. B. Santiago, P. A. Zhizhko, E. N. Bess, J. Varga, G. Frater,
M. S. Sigman, C. Copéret, J. Am. Chem. Soc. 2015, 137, 6699.
[14] a) R. Bosque, C. López, X. Solans, M. Font-Bardia, Organometallics
1999, 18, 1267; b) D. Thiele, R. F. de Souza, J. Mol. Catal. A: Chem.
2011, 340, 83.
a) R. L. Zuckerman, S. W. Krska, R. G. Bergman, J. Am. Chem. Soc.
2000, 122, 751; b) G. K. Cantrell, T. Y. Meyer, J. Am. Chem. Soc. 1998,
120, 8035; c) B. Hamzaoui, J. D. A. Pelletier, E. Abou-Hamad, J.-M.
Basset, Chem. Commun. 2016, 52, 4617; d) S. Barman, N. Merle, Y.
Minenkov, A. De Mallmann, M. K. Samantaray, F. Le Quéméner, K. C.
Szeto, E. Abou-Hamad, L. Cavallo, M. Taoufik, J.-M. Basset,
Organometallics 2017, 36, 1550.
[4]
[5]
a) I. Meisel, G. Hertel, K. Weiss, J. Mol. Catal. 1986, 36, 159; b) K. R.
Birdwhistell, J. Lanza, J. Pasos, J. Organomet. Chem. 1999, 584, 200;
c) T.-G. Ong, G. P. A. Yap, D. S. Richeson, Chem. Commun. 2003,
2612.
a) A. E. Guiducci, C. L. Boyd, P. Mountford, Organometallics 2006, 25,
1167; b) S. C. Dunn, N. Hazari, A. R. Cowley, J. C. Green, P.
Mountford, Organometallics 2006, 25, 1755; c) U. J. Kilgore, F. Basuli,
J. C. Huffman, D. J. Mindiola, Inorg. Chem. 2006, 45, 487; d) D. A.
Kissounko, I. A. Guzei, S. H. Gellman, S. S. Stahl, Organometallics
2005, 24, 5208; e) T. E. Hanna, I. Keresztes, E. Lobkovsky, W. H.
This article is protected by copyright. All rights reserved.

10.1002/anie.201804346
Angewandte Chemie International Edition
COMMUNICATION
Entry for the Table of Contents (Please choose one layout)
Layout 1:
COMMUNICATION
Silica-Supported Ti Imido: Fully
characterized silica-grafted Ti imido
complex enables catalytic
Author(s), Corresponding Author(s)*
Page No. – Page No.
transformations that proceed via
terminal Ti oxo intermediate. Ti-
catalyzed oxo/imido heterometathesis
between N-sulfinylamines and
ketones affords facile syntheses of
hardly accessible by classical
methods ketimines based on bulky or
acid-sensitive ketones and poorly
nucleophilic anilines.
Title
This article is protected by copyright. All rights reserved.