Transfer Hydrocyanation of α- and α,β-Substituted Styrenes Catalyzed by Boron Lewis Acids

Article abstract of DOI:10.1002/anie.201813853

A straightforward gram-scale preparation of cyclohexa-1,4-diene-based hydrogen cyanide (HCN) surrogates is reported. These are bench-stable but formally release HCN and rearomatize when treated with Lewis acids. For BCl₃, the formation of the isocyanide adduct [(CN)BCl₃]^? and the corresponding Wheland complex was verified by mass spectrometry. In the presence of 1,1-di- and trisubstituted alkenes, transfer of HCN from the surrogate to the C?C double bond occurs, affording highly substituted nitriles with Markovnikov selectivity. The success of this transfer hydrocyanation depends on the Lewis acid employed; catalytic amounts of BCl₃ and (C₆F₅)₂BCl are shown to be effective while B(C₆F₅)₃ and BF₃?OEt₂ are not.

Full text of DOI:10.1002/anie.201813853

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Accepted Article
Title: Transfer Hydrocyanation of α- and α,β-Substituted Styrenes
Catalyzed by Boron Lewis Acids
Authors: Patrizio Orecchia, Weiming Yuan, and Martin Oestreich
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of the final Version of Record (VoR). This work is currently citable by
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published online in Early View as soon as possible and may be different
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To be cited as: Angew. Chem. Int. Ed. 10.1002/anie.201813853
Angew. Chem. 10.1002/ange.201813853
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10.1002/anie.201813853
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Transfer Hydrocyanation of α- and α,β-Substituted Styrenes
Catalyzed by Boron Lewis Acids
Patrizio Orecchia+, Weiming Yuan+, and Martin Oestreich*
Abstract: A straightforward gram-scale preparation of cyclohexa-
1,4-diene-based hydrogen cyanide (HCN) surrogates is reported.
These are bench-stable but formally release HCN and rearomatize
when treated with Lewis acids. For BCl3, the formation the
isocyanide adduct [(CN)BCl3]‒ and the corresponding Wheland
complex was verified by mass spectrometry. In the presence of 1,1-
di- and trisubstituted alkenes, transfer of HCN from the surrogate
onto the C‒C double bond occurs, affording highly substituted
nitriles with Markovnikov selectivity. The success of the transfer
hydrocyanation depends on the Lewis acid employed; catalytic
amounts of BCl3 and (C6F5)2BCl are shown to be effective while
B(C6F5)3 and BF3∙OEt2 are not.
capture isocyanide from activated nitriles,[16] we anticipated that
replacement of hydride by cyanide in cyclohexa-1,4-diene-based
surrogates could lead to the related transfer hydrocyanation of
alkenes (Scheme 1, gray box). We report here the development
of such
a transition-metal-free transformation using readily
available HCN surrogates 1 and 2. We note here that, while this
manuscript was in preparation, a related but complementary
methodology employing the same surrogate type was reported
by Studer and co-workers (Scheme 1, bottom).[17] However, that
transfer hydrocyanation is promoted by a palladium catalyst with
the aid of a boron Lewis acid similar to Morandi’s approach,[8a]
eventually leading to the opposite regioselectivity.
Nitriles are synthetically highly versatile as the C≡N functional
group is readily converted into amines or various carbonyl
compounds directly at the desired oxidation level. On an
industrial scale, transition-metal-catalyzed hydrocyanation of
alkenes using hydrogen cyanide (HCN) is the prevalent
methodology to access nitriles.[1] Conversely, the use of
gaseous HCN (b.p. 25.6 °C) in academic laboratories is less
appealing despite the atom economy associated with its addition
across multiple bonds. The severe toxicity of HCN[2] sparked
efforts to identify less volatile surrogates,[3] and acetone
cyanohydrin as well as trimethylcyanide (TMSCN) fulfill this role
in nickel-catalyzed alkene hydrocyanation.[4‒6] Another approach
is based on cobalt catalysis, and this radical process makes use
of solid tosyl cyanide (TsCN) with PhSiH3 as the source of the
hydrogen atom.[7] Morandi and co-workers recently disclosed the
reversible transfer hydrocyanation of alkenes catalyzed by nickel
(Scheme 1, top).[8,9] The equilibrium can be elegantly shifted
toward the right by the release of low-boiling isobutylene.
Our laboratory introduced irreversible transfer processes
catalyzed by B(C6F5)3 where the driving force is the
rearomatization of cyclohexa-1,4-diene surrogates substituted
with an electrofuge at either saturated carbon atom.[10] The
general principle behind this strategy is that the boron Lewis
acid abstracts a hydride from the other saturated position to
generate a Wheland intermediate that eventually releases the
electrofuge.[11] With alkenes as π-basic donor molecules,
transfer hydrosilylation[12] and hydrogenation[13] as well as the
formal transfer of isobutane[14] were realized.[15] As illustrated for
the transfer hydrogenation, the hydrogen atom labeled in red is
transferred as hydride to the more substituted carbon atom and
the hydrogen atom labeled in blue assumes the role of the
proton (Scheme 1, middle). Knowing that B(C6F5)3 is able to
Scheme 1. Transfer hydrocyanation of alkenes.
The preparation of surrogates 1 and 2 was achieved on
gram scale in just one synthetic operation (Scheme 2). Birch
alkylation of benzonitrile (3)[18] and 4-methylbenzonitrile (4) with
methyl iodide as the alkylating reagent afforded 1 and 2 in
isolated yields of 88% and 85%, respectively; 2 is formed as a
mixture of diastereomers but this is irrelevant in the subsequent
transfer process (see the Supporting Information for details).
[*]
P. Orecchia,[+] Dr. W. Yuan,[+] Prof. Dr. M. Oestreich
Institut für Chemie, Technische Universität Berlin
Strasse des 17. Juni 115, 10623 Berlin (Germany)
E-mail: martin.oestreich@tu-berlin.de
Homepage: http://www.organometallics.tu-berlin.de
[+]
These authors contributed equally to this work.
Supporting information for this article is given via a link at the end of
the document.
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6
BCl3[d] (10)
BCl3[d] (20)
BBr3[d] (20)
BF3∙OEt2 (20)
B(OMe)3 (20)
AlCl3 (20)
2
2
2
2
2
1
2
93:7:0
>99 (94)[e]
7
85:13:2
88:11:1
38:62:0
—
40
8
>99 (87)[e]
9
85
0
10
11
12
Scheme 2. One-step preparation of the surrogates.
40:49:11
47:52:1
>99
99
AlCl3 (20)
We chose 1,1-diphenylethylene (5a) as a model substrate
for its propensity to absorb a proton, and stayed with 1,2-F2C6H4
as the solvent (Table 1).[13] However, the transfer process
required significantly higher temperatures than the transfer
hydrogenation[13] and was routinely run at 120 °C (cf. Scheme 1,
middle). Initial experiments with B(C6F5)3 in catalytic or
stoichiometric amounts and employing surrogate 1 were rather
disappointing (entries 1 and 2). The target compound 6a did
form but cationic alkene dimerization yielding 7a prevailed.[19]
Competing hydrogenation furnishing 8a was also seen and is
rationalized by competing hydride abstraction from surrogate 1
by either B(C6F5)3 or the intermediate carbenium ion[11] (see the
Supporting Information for both catalytic cycles). The
hydrogenation pathway was efficiently suppressed using
surrogate 2 which bears an additional methyl substituent at the
former methylene group (entry 3). The use of more Lewis-
acidic[20] BCl3 as catalyst had a dramatic effect on the product
distribution, no matter which of the two surrogates was used
(entries 4‒7). The transfer hydrocyanation proceeded cleanly
with 20 mol% catalyst loading, and 10 mol% were also sufficient
at prolonged reaction time (36 h instead of 16 h). At lower
reaction temperature (80 °C instead of 120 °C), conversion was
low and dimerization began to occur, indicating the cyanide
release from the assumed isocyanoborate intermediate is
probably rate determining. The result with BBr3 was slightly
inferior (entry 8), and BF3∙OEt2 behaved similarly to B(C6F5)3
(entry 9); B(OMe)3 did not facilitate the activation of the
surrogate (entry 10). We briefly examined other Lewis acids
such as AlCl3. However, the desired nitrile 6a and the alkene
dimer 7a were formed in nearly equal amounts (entries 11 and
12). We also note that the choice of the solvent is crucial; there
was no conversion in either benzene or toluene (see the
Supporting Information for the solvent screening).
[a] Unless otherwise noted, all reactions were performed on a 0.10 mmol
scale at 120 °C for 16 h in a sealed tube, using 1.2 equiv of 1 or 2 in 0.5
mL of 1,2-F2C6H4. [b] Estimated by GLC analysis by integration without
calibration. [c] Determined by GLC analysis with tetracosane as an internal
standard. [d] 1.0 M in CH2Cl2. [e] Isolated yield after flash chromatography
on silica gel in parentheses.
We then proceeded to investigate other 1,1-diarylethylenes
with BCl3 as catalyst (Scheme 3). Substitution in both para
positions was generally well tolerated as in 6b‒d except for a
bromo substituent as with 6e. We cannot explain this outcome
but the effect was less pronounced with just one of the aryl
groups brominated as with 6f. A thienyl group as in 6g was also
compatible though the functional-group tolerance was generally
limited. Lewis-basic groups such as nitro (15% NMR yield) and
dibenzylamino (33% NMR yield) thwarted high yields, and no
reaction was observed with substrates containing carbonyl
groups. Moving a methyl group from para to meta to ortho led to
a gradual decrease in yield (6h and 6i versus 6c). We attribute
this to increased steric hindrance, hampering cyanide addition to
the carbenium-ion intermediate. A rigidified version of parent
1,1-diphenylethylene (5a) also reacted smoothly (5j→6j).
H
Me
Me CN
Ar1 Ar2
6b–j
BCl3 (20 mol%)
+
Ar1
Ar2
1,2-F2C6H4
120 °C for 16 h
5b–j
Me CN
2
(1.2 equiv)
Me CN
Me CN
Me CN
MeO
OMe Me
Me F
F
6b: 99%
6c: 83%
Me CN
6d: 94%
Me CN
Me CN
Table 1. Identification of the Lewis acid.[a]
S
Br
Br
Br
6e: 48%
6f: 60%
6g: 65%
Me CN
Me
Me CN
Me CN
Me
6h: 50%
6i: 45%
6j: 68%[a]
Entry
Lewis acid (mol%)
B(C6F5)3 (20)
B(C6F5)3 (100)
B(C6F5)3 (100)
BCl3[d] (20)
Surrogate
6a:7a:8a[b]
42:14:44
20:70:10
18:79:3
99:1:0
Conv. [%][c]
>99
Scheme 3. Scope I: 1,1-Diarylethylenes. All reactions were performed in a
sealed tube charged with 0.10 mmol of alkene 5, 0.12 mmol of surrogate 2
(1.2 equiv), and 20 μL of a 1.0 M solution of BCl3 in CH2Cl2 (20 mol%) in 0.5
mL of 1,2-F2C6H4. [a] Determined by NMR spectroscopy using CH2Br2 as an
internal standard; purification by chromatography failed.
1
2
3
4
5
1
1
2
2
1
>99
>99
>99 (97)[e]
>99
Alkenes other than 1,1-diarylethylenes reacted poorly with
BCl3 as catalyst. We therefore tested (C6F5)BCl2
(C6F5)2BCl[22] as their Lewis acidity[20] falls between that of BCl3
[21]
and
BCl3[d] (20)
94:3:3
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10.1002/anie.201813853
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143.91648
141.91960
and B(C6F5)3 (the role of the substituents at the boron atom is
discussed further below). A 1,1-alkyl/aryl-substituted alkene then
afforded 45% and 72% yield with (C6F5)BCl2 and (C6F5)2BCl,
respectively (Scheme 4, 5k→6k); other styrenes with a linear
alkyl chain in the α position did undergo the aforementioned
dimerization (not shown). (C6F5)2BCl as catalyst then enabled
the transfer hydrocyanation of several trisubstituted alkenes
5l‒q to form 6l‒q containing a nitrile-bearing quaternary carbon
atom (Scheme 4). Yields were consistently high for 1,1-diaryl-
substituted alkenes 5l‒n, and triphenylethylene reacted in 50%
yield (5o→6o). Trisubstituted alkenes with just one aryl group
participated as well (5p and 5q) yet the yield was lower for 5q
with an endocyclic double bond. For comparison, this setup was
also applied to 5a→6a but the reaction was less chemoselective
(gray box). As expected for a reaction that involves the formation
of carbenium ions, 1,2-disubstituted alkenes and α-olefins did
not work.
100
50
145.91342
147.91042
140.92330
141.91949
100
50
0
143.91654
145.91359
140.92312
140
147.91064
130
150
158
m/z
107.08565
100
50
108.08896
100
50
0
107.08553
108.08888
108
106
107
109
m/z
Figure 1. In-situ ESI-MS spectra of [(CN)BCl3]‒ (top) and Wheland
intermediate [C8H11
+ (bottom) at room temperature.
Scheme 4. Scope II: Various di- and trisubstituted alkenes. All reactions were
performed in a sealed tube charged with 0.10 mmol of alkene 5, 0.12 mmol of
surrogate 2 (1.2 equiv), and 20 μL of a 1.0 M solution of (C6F5)2BCl in CH2Cl2
(20 mol%) in 0.5 mL of 1,2-F2C6H4. [a] The ratio of 6a:7a:8a was 68:32:0 (cf.
Table 1).
]
An analysis of the stoichiometric reaction of BCl3 and HCN
surrogate 2 (in form of its two diastereomers) by 11B and 13C
NMR spectroscopy at room temperature provided further
mechanistic insight (Scheme 5). A diagnostic upfield shift from δ
46.5 ppm for BCl3 to δ 5.3 ppm for Lewis adduct 2∙BCl3 was
found in the 11B NMR spectrum.[23] Additional support of the
nitrile coordination came from the 13C NMR spectra of 2∙BCl3;
the Δδ value of ~3.5 ppm is consistent with those previously
described.[23] Heating to 120 °C for a few minutes immediately
led to full degradation of 2 into para-xylene. Neither HCN nor
any isocyano/cyano group could be detected in the 13C NMR
spectrum, possibly because of the quadrupolar effect of the
boron atom. The 11B NMR spectrum showed several resonance
signals at 22.0 and around 5.3 (three) ppm but we could not
assign any of the these to [(CN)BCl3]‒. Hence, we could not
distinguish between the isocyanide adduct [(CN)BCl3]‒ and the
isomeric cyanide [(NC)BCl3]‒. These borates are known to
interconvert, and initially formed [(CN)BCl3]‒ could be in
equilibrium with [(NC)BCl3]‒. However, the isocyanide isomeric is
likely to be favored according to early quantum-chemical
calculations in the gas phase.[24]
The observed regioselectivity is already convincing evidence
for a mechanism involving protonation of the alkene followed by
cyanide addition to the carbenium-ion intermediate. The
Brønsted acid needed for the protonation step would emerge
from abstraction of isocyanide from the HCN surrogate by the
boron Lewis acid. Both the ate complex [(CN)BCl3]‒ derived from
BCl3 and the Wheland intermediate [C8H11]+, that is protonated
para-xylene from 2, were detected by mass-spectrometric
analysis at room temperature (Figure 1).
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Lewis acids help rationalize the distribution between nitrile 6a
and dimerized alkene 7a summarized in Table 1.
We have presented here a new strategy to convert alkenes
into nitriles by transfer hydrocyanation. The HCN molecule is
delivered stepwise from a bench-stable surrogate to the C‒C
double bond by the action of Lewis acid catalyst. The HCN
surrogates are based on adequately substituted cyclohexa-1,4-
dienes that are accessible in gram quantities by Birch reduction
of benzonitriles. The boron Lewis acid abstracts cyanide from
the surrogate, and the resulting Wheland complex protonates
the alkene substrate. The success of the cyanide transfer from
the in-situ-generated isocyanoborate to the carbenium-ion
intermediate largely depends on the borate’s propensity to
isomerize to the cyanoborate. In agreement with a cationic
mechanism, BCl3- or (C6F5)2BCl-catalyzed addition of HCN
across the 1,1-di- and trisubstituted alkenes occurs with
Markovnikov selectivity to afford tertiary nitriles.
Scheme 5. Stoichiometric NMR experiment.
Based on the above findings and literature precedent,[23,24]
we propose a catalytic cycle with three elementary steps for the
transfer hydrocyanation of, e.g., 1,1-diarylethylenes and BCl3 as
catalyst (Scheme 6). The boron Lewis acid abstracts isocyanide
from the HCN surrogate to arrive at the corresponding strongly
acidic Wheland intermediate and the isocyanoborate [(CN)BCl3]‒
(see Figure 1). Subsequent protonation of the alkene by that
strong Brønsted acid leads the more stable carbenium ion
paired with the isocyanoborate counteranion. This step is driven
by the rearomatization of the Wheland intermediate to form
para-xylene. [(CN)BCl3]‒ rather than cyanoborate [(NC)BCl3]‒[24]
then delivers cyanide to the carbenium to close the catalytic
cycle.
Acknowledgements
This research was supported by the Cluster of Excellence
Unifying
Concepts
in
Catalysis
of
the
Deutsche
Forschungsgemeinschaft (EXC 314/2) and the Berlin Graduate
School of Natural Sciences and Engineering (predoctoral
fellowship to P.O., 2016–2019). M.O. is indebted to the Einstein
Foundation (Berlin) for an endowed professorship. We thank Dr.
Maria Schlangen-Ahl and Dr. Sebastian Kemper for expert
advice with the MS and NMR measurements, respectively. Dr.
Elisabeth Irran is acknowledged for the X-ray analysis (all TU
Berlin).
Keywords: alkenes • boron • hydrocyanation • homogeneous
catalysis • Lewis acids
[1]
a) T. V. Rajanbabu, Org. React. 2011, 75, 1‒73; b) L. Bini, C. Müller, D.
Vogt, Chem. Commun. 2010, 46, 8325‒8334; c) L. Bini, C. Müller, D.
Vogt, ChemCatChem 2010, 2, 590‒608; d) C. A. Tolman, J. Chem.
Educ. 1986, 63, 199‒201; e) C. A. Tolman, R. J. McKinney, W. C.
Seidel, J. D. Druliner, W. R. Stevens, Adv. Catal. 1985, 33, 1‒46.
Exposure to 25‒75 ppm for 1 h already shows serious symptoms:
Hydrogen Cyanide In National Institute for Occupational Safety and
Health (NIOSH).
[2]
[3]
[4]
A. M. Nauth, T. Opatz, Org. Biomol. Chem. DOI: 10.1039/C8OB02140F.
a) M. J. Baker, P. G. Pringle, J. Chem. Soc., Chem. Commun. 1991,
1292‒1293; b) M. Yan, Q.-Y. Xu, A. S. C. Chan, Tetrahedron:
Asymmetry 2000, 11, 845‒849; c) M. de Greef, B. Breit, Angew. Chem.
Int. Ed. 2009, 48, 551‒554; Angew. Chem. 2009, 121, 559‒562.
A. Falk, A.-L. Göderz, H. G. Schmalz, Angew. Chem. Int. Ed. 2013, 52,
1576‒1580; Angew. Chem. 2013, 125, 1617‒1621.
Scheme 6. Elementary steps of the catalytic cycle.
[5]
[6]
The nature of the boron Lewis acid affects both the
isocyanide abstraction and the cyanide transfer. Importantly, the
substituents at the boron atom also influence the crucial
isocyanide/cyanide isomerization that occurs between these
steps.[24] A bias away from the isocyanoborate and toward the
cyanoborate could retard the final step of the catalytic cycle, at
the same time providing the opportunity for the carbenium ion to
react with another alkene molecule (Scheme 6, off-cycle
dimerization in gray box). For BCl3 and (C6F5)2BCl,
isocyanoborate binding is favored whereas the cyanoborate is
preferred with B(C6F5)3 and BF3∙OEt2. Consequently, the dimer
is seen in substantial amounts with the latter Lewis acids as well
as AlCl3 as catalysts. The recently computed, thermodynamically
downhill flip of [(CN)B(C6F5)3]‒ to [(NC)B(C6F5)3]‒[16] lends further
support to this mechanistic picture. These properties of the
These surrogates display toxicity similar to HCN: a) W. C. Groutas,
Cyanotrimethylsilane in e-EROS Encyclopedia of Reagents for Organic
Synthesis, 2001; b) S. A. Haroutounian, Acetone cyanohydrin in e-
EROS Encyclopedia of Reagents for Organic Synthesis. 2001.
B. Gaspar, E. M. Carreira, Angew. Chem. Int. Ed. 2007, 46,
4519‒4522; Angew. Chem. 2007, 119, 4603‒4606.
[7]
[8]
a) X. Fang, P. Yu, B. Morandi, Science 2016, 351, 832–836; for a
computational analysis of the reaction mechanism, see: b) S.-F. Ni, T.-L.
Yang, L. Dang, Organometallics 2017, 36, 2746‒2754.
[9]
For recent reviews of transition-metal-catalyzed transfer processes,
see: a) B. N. Bhawal, B. Morandi, Angew. Chem. Int. Ed. DOI:
10.1002/anie.201803797;
Angew.
Chem.
DOI:
10.1002/ange.201803797; b) B. N. Bhawal, B. Morandi, Chem. Eur. J.
2017, 23, 12004–12013; c) B. N. Bhawal, B. Morandi, ACS Catal. 2016,
6, 7528–7535.
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[10] For a review, see: S. Keess, M. Oestreich, Chem. Sci. 2017, 8, 4688–
4695.
[11] For a comprehensive quantum-chemical analysis of various reaction
pathways, see: a) S. Banerjee, K. Vanka, ACS Catal. 2018, 8, 6163–
6176; for relevant experimental work suggesting competing reaction
pathways, see: b) I. Chatterjee, M. Oestreich, Org. Lett. 2016, 18,
2463–2466.
[12] For a review of transfer hydrosilylation, see: a) M. Oestreich, Angew.
Chem. Int. Ed. 2016, 55, 494–499; Angew. Chem. 2016, 128, 504‒509;
b) A. Simonneau, M. Oestreich, Angew. Chem. Int. Ed. 2013, 52,
11905–11907; Angew. Chem. 2013, 125, 12121‒12124; c) A.
Simonneau, M. Oestreich, Nat. Chem. 2015, 7, 816–822; for
a
computational analysis of the reaction mechanism, see: d) K. Sakata, H.
Fujimoto, Organometallics 2015, 34, 236–241.
[13] I. Chatterjee, Z.-W. Qu, S. Grimme, M. Oestreich, Angew. Chem. Int.
Ed. 2015, 54, 12158–12162; Angew. Chem. 2015, 127, 12326‒12330.
[14] S. Keess, M. Oestreich, Chem. Eur. J. 2017, 23, 5925–5928.
[15] For related transfer processes using cyclohexa-1,3-diene-based
surrogates, see: W. Yuan, P. Orecchia, M. Oestreich, Chem. Commun.
2017, 53, 10390–10393.
[16] J. Li, Y. Okuda, J. Zhao, S. Mori, Y. Nishihara, Org. Lett. 2014, 16,
5220‒5223.
[17] A. Bhunia, K. Bergander, A. Studer, J. Am. Chem. Soc. 2018, 140,
16353–16359.
[18] K. Ohkata, Y. Tamura, B. B. Shetuni, R. Takagi, W. Miyanaga, S.
Kojima, L. A. Paquette, J. Am. Chem. Soc. 2004, 126, 16783‒16792.
[19] a) For the computed pathway of its formation, see Ref. [13]; b) for its
subsequent formation in high yield, see: J. Möbus, T. vom Stein, D. W.
Stephan, Chem. Commun. 2016, 52, 6387–6390.
[20] I. B. Sivaev, V. I. Bregadze, Coord. Chem. Rev. 2014, 270‒271, 75‒88.
[21] A. Sundararaman, F. A. Jäkle, J. Organomet. Chem. 2003, 681,
134‒142.
[22] D. J. Parks, W. E. Piers, G. P. A. Yap, Organometallics 1998, 17,
5492‒5503.
[23] For a useful discussion of the 11B and 13C chemical shifts of three- and
four-coordinate boron compounds with and without C≡N ligands, see: A.
Bernsdorf, H. Brand, R. Hellmann, M. Köckerling, A. Schulz, A. Villinger,
K. Voss, J. Am. Chem. Soc. 2009, 131, 8958‒8970.
[24] D. S. Marynick, L. Throckmorton, R. Bacquet, J. Am. Chem. Soc. 1982,
104, 1‒5.
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Suggestion for the Entry for the Table of Contents
COMMUNICATION
P. Orecchia, W. Yuan, M. Oestreich*
Page No. – Page No.
Transfer Hydrocyanation of α- and
α,β-Substituted Styrenes Catalyzed
by Boron Lewis Acids
Acid-free! Bench-stable cyclohexa-1,4-diene-based hydrogen cyanide (HCN)
surrogates are reported to engage in transfer hydrocyanation of alkenes by
treatment with certain boron Lewis acids. The success also depends on the
equilibrium position between the intermediate isocyano- and cyanoborate isomers.
Tertiary nitriles are obtained with exclusive Markovnikov selectivity (see scheme).
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