Enantioselective rhodium-catalysed insertion of trifluorodiazoethanes into tin hydrides

Article abstract of DOI:10.1016/j.tet.2018.11.022

Aryl substituted 2,2,2-trifluorodiazoethanes undergo rhodium(II)-catalysed insertion reactions with tin hydrides affording the corresponding α-(trifluoromethyl)benzyl stannanes. This reactivity contrasts with that of diazo esters which predominantly afford CH₂ reduction products in the presence of tin hydrides. The first example of asymmetric insertion into tin hydrides using diazo compounds is also described. In addition, this system extends to asymmetric germanium hydride and silane insertion.

Full text of DOI:10.1016/j.tet.2018.11.022

Accepted Manuscript
Enantioselective rhodium-catalysed insertion of trifluorodiazoethanes into tin hydrides
Stephen Hyde, Janis Veliks, David M.H. Ascough, Robert Szpera, Robert S. Paton,
Véronique Gouverneur
PII:
S0040-4020(18)31362-0
https://doi.org/10.1016/j.tet.2018.11.022
TET 29933
DOI:
Reference:
To appear in: Tetrahedron
Received Date: 18 September 2018
Revised Date: 5 November 2018
Accepted Date: 10 November 2018
Please cite this article as: Hyde S, Veliks J, Ascough DMH, Szpera R, Paton RS, Gouverneur Vé,
Enantioselective rhodium-catalysed insertion of trifluorodiazoethanes into tin hydrides, Tetrahedron
(2018), doi: https://doi.org/10.1016/j.tet.2018.11.022.
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ACCEPTED MANUSCRIPT
Enantioselective rhodium-catalysed insertion of
trifluorodiazoethanes into tin hydrides
Stephen Hyde, Janis Veliks, David M. H. Ascough, Robert Szpera, Robert S. Paton, Véronique Gouverneur*
Leave this area blank for abstract info.

ACCEPTED MANUSCRIPT
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Enantioselective rhodium-catalysed insertion of trifluorodiazoethanes into tin hydrides
Stephen Hyde,a Janis Veliks,a David M. H. Ascough,a Robert Szpera,a Robert S. Paton,a,b Véronique Gouverneur*a
[a]Department of Chemistry, University of Oxford, Chemistry Research Laboratory, Mansfield Road, OX1 3TA, UK [b] Department of Chemistry, Colorado State University, Fort Collins, CO 80523, USA.
AB ST R ACT
AR T ICL E INFO
Article history:
Received
Aryl substituted 2,2,2-trifluorodiazoethanes undergo rhodium(II)-catalysed insertion reactions with tin hydrides affording
the corresponding α-(trifluoromethyl)benzyl stannanes. This reactivity contrasts with that of diazo esters which
predominantly afford CH2 reduction products in the presence of tin hydrides. The first example of asymmetric insertion
into tin hydrides using diazo compounds is also described. In addition, this system extends to asymmetric germanium
hydride and silane insertion.
Received in revised form
Accepted
Available online
Keywords:
Stannane
Asymmetric insertion
trifluorodiazoethane
Silane
2009 Elsevier Ltd. All rights reserved.
Germanium hydride
reported conditions,21 involving slow addition over one hour of diazo
compound to a mixture of Cu(MeCN)4PF6 (4 mol%) and tributyltin hydride (2
1. Introduction
The insertion of diazo compounds into carbon-hydrogen and heteroatom-
hydrogen bonds is well-documented.1,2,3,4 Insertion reactions where X-H (X =
C, Si, S, O, N, B, P) bonds are cleaved by Rh, Cu, or other metal carbenoid
intermediates, have been well studied both in racemic5,6,7,8,9,10,11 and
asymmetric12,13 settings. Insertion into trialkyltin hydrides has received
relatively little attention, despite several early reports supporting the
feasibility of such insertion with carbenes.14,15,16 In 1995, Landais and co-
workers reported an isolated example of trialkyltin hydride insertion with
diazo esters (Figure 1a).17 Wang later showed that tin hydride enables the
reduction of diazo carbonyl compounds, a process resulting from in situ
protodestannylation of the tin hydride insertion product (Figure 1b).18. More
recently, the groups of Wang and Bi have disclosed insertion into the Sn-H
bond leading to stable benzyltributylstannanes.19,20 Both methods generate
the diazo intermediate in situ from a tosyl- or nosylhydrazone, however
neither system offer a route to asymmetric insertion (Figure 1c and 1d). Our
group extended X-H insertion to trifluorodiazoalkanes.21 Under Cu catalysis,
Si-H, S-H, N-H, B-H, and P-H bonds were successfully cleaved, and an
asymmetric protocol was developed for silanes and boranes (Figure 1e).
However, tributyltin hydride gave a low yield of the insertion product under
our standard reaction conditions. Herein, we report the successful
development of a rhodium catalyzed tributyltin hydride insertion with aryl-
substituted 2,2,2-trifluorodiazoethanes, as well as extension to an
asymmetric catalytic protocol (Figure 1f). This system is also suitable for
asymmetric insertion into germanium hydrides and silanes.
equivs), only 26% of the desired product 2a was obtained, in addition to the
2. Results and discussion
The starting materials for this study, aryl-substituted 2,2,2-
trifluorodiazoethanes, were prepared according to previously reported
literature procedures.22,23 Optimization studies of the tributyltin hydride
insertion reaction were performed using 4-(1-diazo-2,2,2-trifluoroethyl)-1,1'-
biphenyl (1a) as the model substrate (Table 1). Under our previously
reduced product.

2
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Figure 1. Sn-H insertion reactions with trialkyltin hydrides
insertion products 2. The limitations for this transformation are highlighted
by the electron rich methoxy- substituted substrate 1j which gives a low
yield of 38%. This procedure was also efficient for PhMe2SiH and nBu3GeH
insertion, delivering silane 2m and organogermanium 2n in good yields.
(Table 1, entry 1). Decreasing the amount of nBu3SnH to 1.0 equivalents and
changing the order of addition were not beneficial (Table 1, entries 2 and 3).
Under Rh2(OAc)4 catalysis, comparably poor results were obtained (entry 4).
When the reaction was performed by fast addition of Rh(II) catalyst to an
equimolar mixture of diazo compound 1a and nBu3SnH in dichloromethane
in an open vial, almost instantaneous evolution of nitrogen and
disappearance of the characteristic orange colour of the diazo compound 1a
was observed (Table 1, entry 5). The desired insertion product 2a was
isolated in 64% yield. Cu(II) and Rh(I) were ineffective for this transformation
(entries 6 and 7). Screening various solvents highlighted dichloromethane as
the optimum solvent for Sn-H insertion (entry 5 vs. entries 8-11).
Table 1. Optimization studies for Sn-H insertion[a]
Entry
1[b]
Catalyst
Cu(MeCN)4PF4
Solvent
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CHCl3
Procedure[c]
Yield[d]
26
A
B
C
A
C
C
C
C
C
C
C
D
D
D
2
Cu(MeCN)4PF4
Cu(MeCN)4PF4
Rh2(OAc)4
Rh2(OAc)4
Cu(OAc)2
4
3
traces
25
4
5
64
6
traces
(6)
7
Rh(PPh)3Cl
Rh2(OAc)4
Rh2(OAc)4
Rh2(OAc)4
Rh2(OAc)4
Rh2(OAc)4
8
(43)
(59)
(43)
(45)
74
9
Toluene
Hexane
DCE
10
11
12
13
14
Scheme 1. Rhodium-catalysed insertion into Sn-H bonds with aryl substituted
trifluorodiazoethanes. All reactions performed on 0.1 mmol scale following procedure D
(table 1) unless stated otherwise. All yields are those of isolated products. [a] Procedure
C. [b] 1.0 eq. of PhMe2SiH instead of nBu3SnH. [c] 1.0 eq. of nBu3GeH instead of
nBu3SnH.
CH2Cl2
CH2Cl2
CH2Cl2
[e]
Rh2(OAc)4
67
[f]
Rh2(OAc)4
74
[a] All reactions performed on a 0.1 mmol scale with 1.0 eq. of 1a and nBu3SnH, with
4.0 mol% catalyst loading, unless stated otherwise. [b] 2.0 eq. of nBu3SnH. [c]
Procedure A: Syringe pump addition of 1a solution to a mixture of cat. and nBu3SnH in
dichloromethane over 1h. Procedure B: Syringe pump addition of 1a and nBu3SnH
solution to a catalyst suspension in dichloromethane over 1h. Procedure C: 1a and
nBu3SnH added to vial and dissolved in dichloromethane (not degassed). The catalyst
was then added. Procedure D: 1a and nBu3SnH added to a vial and dissolved in
dichloromethane under anhydrous conditions. In a separate vial was added the catalyst
and dichloromethane. The mixture of 1a and nBu3SnH was added to the catalyst
suspension. [d] All yields are those of isolated products unless stated otherwise. 1H and
19F NMR yields, using ethyl trifluoroacetate as internal reference, are shown in
parenthesis. [e] 2 mol% of catalyst. [f] 10 mol% of catalyst.
When these reaction conditions were applied to diazo esters 3a and 3b, the
crude 1H NMR spectra indicated mixtures of stannanes 4 and reduction
products 5, and upon workup, only the latter were isolated (scheme 2).
These examples highlight the instability of α-carbonyl stannanes, which is
consistent with previous literature.18
When the reaction was performed under an argon atmosphere with
degassed dichloromethane, and the reagent mixture quickly transferred to
the catalyst under inert atmosphere, the yield of the desired product 2a was
further improved to 74% (entry 12). The use of 4 mol% of Rh2(OAc)4 was
optimal for this transformation (entry 12 vs. 13 and 14).
Scheme 2. Reactivity of diazo esters towards nBu3SnH
Given that Wang proposed that α-carbonyl stannanes undergo
protodestannylation via a putative radical pathway, radical stabilization
enthalpies (RSE), which are derived from bond dissociation enthalpies (BDE),
may account for the difference in stability of the stannane products. Due to
After optimisation of the reaction conditions, the substrate scope was
investigated. Various substituents such as alkyl, aryl, halide, and CF3 are
tolerated on the phenyl group giving good to moderate yields of the

the paucity of experimental tin bond dissociation enthalpies, we performed
Table 3. Optimization studies for asymmetric insertion 1a into nBu3SnH[a]
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quantum mechanical calculations in Gaussian 09 rev. D.0.1.24 Computation
of tin bond dissociation enthalpies is challenging, due to relativistic effects,
and lack of experimental data for benchmarking. Grindley and Boyd have
benchmarked organotin bond dissociation energies, finding a strong method
dependence; we use the B3LYP/SDB-aug-cc-pVTZ//B3LYP/def2-SVPD level of
theory described by the latter.25,26 We also computed the corresponding
proto derivatives using the higher G4 method for comparison and confirm
good correlation of RSEs (see SI).27
Entry
Procedure Catalyst
T/ oC
Yield 2a/ %
ee/ %
1
2
3
4
A
A
A
A
Rh2(S-DOSP)4
RT
RT
RT
RT
78
19
78
36
7
Rh2(R-PTAD)4
Rh2(R-BTPCP)4
Rh2(S-tertPTTL)4
79
-26
-90
5
B
B
B
Rh2(S-tertPTTL)4
Rh2(S-tertPTTL)4
Rh2(S-tertPTTL)4
RT
0
-78
82
74
57
-91
-92
-94
Table 2. Computed bond enthalpies in kcal/mol[a]
6
7[c]
Entry Stannane R1
R2
BDE RSE
1
2
3
4
5
6a
6b
6c
6d
6e
H
H
H
63.6 0.0 (defined)
58.6 5.0
Yields are those of isolated products. [a] Procedure A: Diazo and stannane added to vial
and dissolved in dichloromethane. To the mixture was added the catalyst. Procedure B:
CO2Et
C6H5 CF3
C6H5 CH3
47.2 16.4
(anhydrous conditions) Diazo and stannane added to
a vial and dissolved in
41.8 21.8
dichloromethane. In a separate vial was added the catalyst and more dichloromethane.
The diazo/stannane mixture was added to the catalyst suspension. [c] Reaction time 30
minutes.
C6H5 CO2Me 42.7 20.9
[a] Values computed at the B3LYP/SDB-aug-cc-pVTZ//B3LYP/def2-SVPD level of
theory, BDE – bond dissociation enthalpy, RSE – radical stabilization energy.
Comparable results were achieved when electron poor ester 1c and electron
rich 4-methoxy substituted diazo compound 1j were subjected to the
asymmetric insertion protocol, affording stannanes 2c and 2j with good to
moderate yields with good enantioselectivities. In addition, these optimized
reaction conditions were highly efficient for PhMe2SiH and nBu3GeH
asymmetric insertion, affording silane 2m and organogermanium 2n in good
and excellent yields respectfully, both with 99% ee (scheme 3).
Of the compounds calculated, the RSE corresponding to stannane 6b (5.0
kcal/mol) is lower than the other compounds investigated by at least 10
kcal/mol (Table 2, entry 2). This is consistent with the low propensity for this
compound to undergo protodestannylation via
a radical pathway. In
contrast, the phenyl-substituted ester 6e has a much higher RSE (20.9
kcal/mol) consistent with the protodestannylation observed experimentally
(Table 2, entry 5).18 Compound 6c has significantly lower RSE than the non-
fluorinated derivative 6d with RSEs of 16.4 kcal/mol and 21.8 kcal/mol
respectively (Table, entries 3 and 4). This is consistent with reports of the
destabilizing effect of trifluoromethyl substitution on carbon-centered
radicals.28 Additionally, we find the RSE corresponding to 6d and the phenyl
substituted ester 6e to be similar (RSE = 21.8 kcal/mol and 20.9 kcal/mol
respectively).
Despite asymmetric heteroatom-hydrogen insertion reactions with diazo
compounds having been extensively studied for many nucleophiles,12 to date
there are no examples of catalytic enantioselective Sn-H insertion reactions.
This is possibly due to α-diazo carbonyl compounds generating unstable
stannane insertion products.18 Since aryl 2,2,2-trifluorodiazoethanes are
converted into stable Sn-H insertion products, we sought to develop an
asymmetric protocol.
Optimization studies for an asymmetric insertion reaction were performed
by testing a range of chiral Rh(II) catalysts (Table 3, entries 1 to 4). For
operational simplicity, the chiral catalyst was added to a solution of diazo
compound 1a and tributyltin hydride in dichloromethane in an open vial, a
process which allowed for the rapid identification of Rh2(S-tertPTTL)4 as the
most efficient catalyst affording 2a in 90% ee but low yield (entry 4).29,30
When the reaction was performed under inert atmosphere in degassed
solvent, a significant improvement of yield was achieved in addition to slight
increase of enantioselectivity (entry 5). Decreasing temperature improved
ee, however the yield was diminished (entries 6 and 7). At -78 oC,
enantioenriched stannane 2a was isolated in 57% yield and 94% ee.
Scheme 3. Asymmetric rhodium-catalysed insertion into X-H bonds (X = Sn,
Ge, Si) with trifluorodiazoethanes. Absolute configuration determined by
comparison of [α]D value of 2m with that reported in the literature.21
Absolute configuration of other substrates assigned by analogy with 2m.
3. Conclusion
In summary, we have developed a Rh(II) catalysed trialkyltin hydride
insertion reaction into 1-aryl-2,2,2-trifluorodiazoethanes. In contrast to
products of Sn-H insertion of α-carbonyl diazo compounds, the α-
(trifluoromethyl)benzyl stannanes are bench stable. In addition, the first
asymmetric tin hydride insertion with diazo compounds has been disclosed
delivering enantioenriched α-(trifluoromethyl)benzyl stannanes. The use of
the stannane products in palladium catalyzed cross coupling is challenging
due to their propensity to undergo β-fluoride elimination. However, a recent
report has demonstrated that secondary α-(trifluoromethyl)benzyl tosylates

4
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can undergo cross coupling without β-fluoride elimination, suggesting that
the same might possible for the corresponding stannanes disclosed within.31
NaHCO3 and brine, dried with MgSO4, concentrated under reduced pressure,
and purified by silica gel chromatography.
4. Experimental
General procedure C: telescoped preparation of diazo substrates 1
4.1 General Information
CAUTION: diazo compounds are presumed to be toxic and potentially
explosive and should be handled with care, in a fume hood.34 To a mixture of
tosyl hydrazine (1.0 eq.) in MeOH (1.5 M) was added ketone (1.0 eq). The
reaction mixture was heated to reflux for 18 h then allowed to cool to room
temperature. Solvent was evaporated under reduced pressure and the
residue triturated with pentane, dried under vacuum and used in
subsequent steps without additional purification. To the residue was added
KOH (2.0 equiv.) in MeOH (0.4 M) and the reaction mixture heated to reflux
for 1–2 hours, during which the characteristic red colour of diazo
compounds appeared. The reaction mixture was allowed to cool to room
temperature, poured into water and extracted with pentane (x3). The
combined organic layers were dried over Na2SO4, filtered and evaporated
under reduced pressure. The residue was purified by silica gel column
chromatography.
All NMR spectra were recorded on Bruker DPX200, AV400 or AV500
spectrometers and are reported as chemical shifts (δ) in parts per million
(ppm). 1H and 13C NMR spectra are referenced relative to residual
undeuterated solvent peak. 19F NMR spectra are referenced relative to CFCl3.
Coupling constants (J) are reported in units of hertz (Hz). The following
abbreviations are used to describe multiplets: s (singlet), d (doublet), t
(triplet), q (quartet), quint (quintuplet), sept (septet), m (multiplet), br
(broad). High resolution mass spectra (HRMS, m/z) were recorded on a
Bruker MicroTOF spectrometer using electrospray ionization (ESI), electron
ionisation (EI) or chemical ionisation (CI). Infrared spectra were recorded as
neat compound using a Bruker Tensor 27 FT-IR spectrometer. Absorptions
are reported in wavenumbers (cm-1) and only peaks of interest are reported.
Melting points of solids were measured on a Griffin apparatus and are
uncorrected. Thin layer chromatographies (TLC) were performed using
Merck aluminium-foil baked plates precoated with Kieselgel 60 F254. The
products were visualized using UV fluorescence (254 nm) or potassium
permanganate stain. Flash column chromatography columns were
performed over Merck silica gel C60 (40 60 µm) using eluent systems as
described for each experiment. All solvents and chemicals were purchased
from Sigma-Aldrich, Acros, Alfa Aesar, Fluorochem or Apollo Scientific, and
used without further purification, unless stated otherwise.
N'-(1-([1,1'-biphenyl]-4-yl)-2,2,2-trifluoroethylidene)-4-
methylbenzenesulfonohydrazide (1’a)
Prepared following general procedure
A from the corresponding
trifluoroacetophenone (6.7 g, 36 mmol.), in toluene (90 °C, 12 h). Purified by
precipitation upon cooling to room temperature and subsequent filtration.
Obtained as an off-white solid (11.4 g, 76 %). 1H NMR (400 MHz, CDCl3) δ
3
3
8.09 (s, 1H), 7.84 (d, JHH = 8.3 Hz, 2H), 7.73 (d, JHH = 8.3 Hz, 2H), 7.60 (m,
2H), 7.50 (m, 2H), 7.43 (m, 1H), 7.35 (m, 3H), 2.47 (s, 3H). 13C NMR (100 MHz,
4.2 Preparation of diazo substrates 1
2
All diazo compounds
1 were prepared from the corresponding
CDCl3) δ 145.2, 144.7, 141.6 (q, JCF = 35.7 Hz), 139.7, 134.7, 130.1, 129.3,
1
128.9, 128.8, 128.6, 128.2, 127.4, 124.0, 120.2 (q, JCF = 271 Hz), 21.9. 19F
trifluoroacetophenones, either via general procedure A followed by general
procedure B, or in a telescoped process using general procedure C. The
trifluoroacetophenones were prepared according to literature
procedures.23,32
NMR (376 MHz, CDCl3) δ -68.1 (s, 3F). Data consistent with literature
values.23
4-(1-diazo-2,2,2-trifluoroethyl)-1,1'-biphenyl (1a)
General procedure A: preparation of hydrazone diazo precursors 1’
Prepared following general procedure B from tosylhydrazone 1’a (7.41 g,
Procedure from Wang et al.33 To a round bottom flask equipped with a reflux
condenser was added tosylhydrazide (1.0 eq.) and the minimum quantity of
solvent (either methanol or toluene according to individual substrates)
needed to dissolve the hydrazide at reflux (approximately 1.5 M).
Subsequently the reaction was cooled to room temperature and
trifluoroacetophenone (1.0 eq.) was added in one portion. The reaction
mixture was then stirred at 65 °C (MeOH) or 90 °C (Toluene) over 4-16 h
(monitored by TLC). The solution was cooled to room temperature or 0 °C, at
which point the product precipitated out of solution (precipitation can be
induced by addition of pentane). The precipitate was collected by vacuum
filtration and washed with pentane, in which case it was used without
further purification. If no precipitation occurred, the solvent was removed
under reduced pressure and the residue used in the next step without
further purification. Hydrazone derivatives were found to be unstable on
silica gel.
17.1 mmol). Purified by silica gel chromatography (pentane) and obtained as
1
a orange/red solid (1.86 g, 40 %). H NMR (400 MHz, CDCl3) δ 7.39 (m, 2H),
3
7.29 (m, 2H), 7.23 (m, 2H), 7.14 (m, 1H), 6.81 (d, JHH = 8.1 Hz, 2H). 13C NMR
(126 MHz, CDCl3) δ 129.2, 128.0, 127.9, 127.7, 127.6, 126.3 (q, 1JCF = 270 Hz),
125.6, 123.2, 122.1 (C=N2 not observed). 19F NMR (376 MHz, CDCl3) δ -57.4
(s, 3F). Data consistent with literature values.36
N'-(1-(4-bromophenyl)-2,2,2-trifluoroethylidene)-4-
methylbenzenesulfonohydrazide (1’b)
Prepared following general procedure
A
from 4’-bromo-2,2,2-
trifluoroacetophenone (2.43 g, 9.6 mmol.) in toluene (90 °C, 12 h). Purified
by precipitation upon cooling to room temperature and subsequent
filtration. Obtained as an off-white solid (3.72 g, 74%). 1H NMR (400 MHz,
3
CDCl3) δ 7.90 (s, 1H) 7.81 (m, 2H), 7.60 (m, 2H), 7.36 (d, JHH = 7.8 Hz, 2H),
3
7.15 (d, JHH = 7.8 Hz, 2H), 2.47 (s, 3H). 13C NMR (100 MHz, CDCl3) δ 145.3,
2
140.5 (q, JCF = 36.0 Hz), 134.5, 133.7, 130.1, 130.0, 128.4, 126.8, 124.3,
General procedure B: preparation of diazo substrates 1
1
120.0 (q, JCF = 273 Hz), 21.9. 19F NMR (376 MHz, CDCl3) δ -68.2 (s, 3F). Data
consistent with literature values.33
CAUTION: diazo compounds are presumed to be toxic and potentially
explosive and should be handled with care, in a fume hood.34 Procedure
from Xu et al.35 The Tosyl hydrazone (1.0 eq.) was refluxed in a solution of
KOH (2 eq.) in MeOH (0.4 M) for 1 h or until the colour of the solution no
longer intensified. The reaction was then cooled to room temperature and
diluted with water. The crude product was extracted with CH2Cl2 or pentane
(see individual substrates for details), washed with saturated solutions of
1-bromo-4-(1-diazo-2,2,2-trifluoroethyl)benzene (1b)
Prepared following general procedure B from tosylhydrazone 1’b (3.5 g, 8.3
mmol.). Purified by silica gel chromatography (pentane) and obtained as a

1
deep-red liquid (1.21 g, 55 %). 1H NMR (400 MHz, CDCl3) δ 7.51 (m, 2H), 6.97
(q, JCF = 269.3 Hz), 124.7, 123.5, 120.4, (C=N2 not observed). 19F NMR (471
ACCEPTED MANUSCRIPT
(d, JHH = 8.6 Hz, 2H). 13C NMR (100 MHz, CDCl3) δ 132.5, 125.7 (q, JCF = 270
Hz), 123.8, 122.9, 119.7 (C=N2 not observed). 19F NMR (376 MHz, CDCl3) δ -
57.6 (s, 3F). Data consistent with literature values.23
MHz, C6D6) δ -57.5 (s, 3F). IR (neat) υ/ cm-1: 3071, 2082, 1594, 1561, 1481,
1349, 1324, 1261, 1172, 1106, 993, 968, 860, 773, 760, 710, 700, 678.39
3
1
4-methyl-N'-(2,2,2-trifluoro-1-phenylethylidene)benzenesulfonohydrazide
(1’f)
methyl-4-(2,2,2-trifluoro-1-(2-tosylhydrazineylidene)ethyl)benzoate (1’c)
Prepared following general procedure A from trifluoroacetophenone (2.09 g,
12 mmol.), in methanol (65 °C, 12 h). Purified by precipitation upon cooling
to room temperature and subsequent filtration. Obtained as an off-white
solid (2.79 g, 68%). 1H NMR (400 MHz, CDCl3) δ 7.92 (s, 1H) 7.81 (m, 2H),
Prepared following general procedure
A
from corresponding
trifluoroacetophenone (3.0 g, 12.9 mmol.) in toluene (90 °C, 12 h). Purified
by precipitation upon cooling to room temperature and subsequent
filtration. Obtained as an off-white solid (4.36 g, 85%). 1H NMR (400 MHz,
CDCl3) δ 7.96, (s, 1H), 7.84 (m, 2H), 7.35 (m, 4H), 7.15 (d, 2H), 2.49 (s, 3H),
3
7.50 (m, 3H), 7.35 (d, JHH = 8.0 Hz, 2H), 7.25 (m, 2H), 2.47 (s, 3H). 13C NMR
(100 MHz, CDCl3) δ 145.1, 141.4 (q, 2JCF = 35.7 Hz), 134.6, 130.1, 130.1, 128.3,
128.1, 125.3, 120.1 (q, 1JCF = 273 Hz), 21.8 (unable to see C=N2). 19F NMR (376
MHz, CDCl3) δ -68.2 (s, 3F). Data consistent literature values.22
2
2.40 (s, 3H). 13C NMR (100 MHz, CDCl3) δ 165.4, 145.0, 140.4 (q, JCF = 36.5
Hz), 134.5, 133.2, 131.2, 130.0, 129.7, 128.6, 128.2, 120.0 (q, 1JCF = 273.0 Hz),
53.0, 21.9. 19F NMR (376 MHz, CDCl3) δ -68.1 (s, 3F). Data consistent with
literature values.23
(1-diazo-2,2,2-trifluoroethyl)benzene (1f)
Prepared following general procedure B from tosylhydrazone 1’f (2.91 g, 8.5
methyl 4-(1-diazo-2,2,2-trifluoroethyl)benzoate (1c)
mmol.). Purified by silica gel chromatography (pentane) and obtained as a
1
volatile red liquid (544 mg, 35 %). H NMR (400 MHz, C6D6) δ 7.42 (m, 2H),
Prepared following a modification of general procedure B: To a solution of
tosylhydrazone 1’c (1.12 g, 2.8 mmol.) in MeOH (10 mL) was added NaOMe
(303 mg, 5.6 mmol., 2 eq.). A condenser was attached, and the reaction
mixture refluxed for 1 h. The reaction was cooled to room temperature and
diluted with water. The crude product was extracted with CH2Cl2, washed
with saturated solutions of NaHCO3 and brine, dried with MgSO4,
concentrated under reduced pressure, and purified by silica gel
chromatography (pentane/CH2Cl2 90:10) and obtained as an orange solid
3
7.21 (m, 1H), 7.12 (d, JHH = 8.2 Hz, 2H). 13C NMR (126 MHz, C6D6) δ 130.0,
1
126.7 (q, JCF = 269 Hz), 126.5, 123.9, 122.9 (C=N2 not observed). 19F NMR
(376 MHz, C6D6) δ - 57.3 (s, 3F). Data consistent with literature values.22
4-methyl-N'-(2,2,2-trifluoro-1-(4-
fluorophenyl)ethylidene)benzenesulfonohydrazide (1’g)
1
3
(414 mg, 63 %). H NMR (400 MHz, CDCl3) δ 8.05 (d, JHH = 8.8 Hz, 2H), 6.73
Prepared
following
general
procedure
A
from
2,2,2,4'-
3
(d, JHH = 8.8 Hz, 2H), 3.60 (s, 3H). 13C NMR (126 MHz, CDCl3) δ 132.4, 126.3,
tetrafluoroacetophenone (1.0 g, 5.20 mmol.) in methanol (65 oC, 12 h).
Purified by cooling to room temperature and subsequent filtration and
washing with pentane. Obtained as a white solid (1.45 g, 77 %). Used
without further purification. 1H NMR (400 MHz, CDCl3): δ 7.98 (s, 1H), 7.80
(d, J = 8.3 Hz, 2H), 7.36 (d, J = 8.0 Hz, 2H), 7.29-7.19 (m, 4H), 2.46 (s, 3H). 13C
125.2 (q, 1JCF = 269.0 Hz), 124.1, 123.3, 122.5, 119.2 (C=N2 not observed). 19
F
NMR (376 MHz, CDCl3) δ -57.5 (s, 3F). Data consistent with literature
values.23
1
NMR (101 MHz, CDCl3): δ 164.2 (d, JCF = 252.7 Hz), 145.2, 134.5, 130.9,
1
4-methyl-N'-(2,2,2-trifluoro-1-(p-tolyl)ethylidene)benzenesulfonohydrazide
130.8, 130.0, 128.2, 120.1 (q, JCF = 274.9 Hz), 117.7, 117.5, 21.8. 19F NMR
(1’d)
(377 MHz, CDCl3): δ -68.4 (s, 3F), -106.6 (m, 1F). Data consistent with
literature values.33
Prepared following general procedure
A
from 2,2,2-trifluoro-1-(p-
tolyl)ethan-1-one (1.0 g, 5.31 mmol.) in methanol (65 oC, 18 h). Purified by
cooling to room temperature and subsequent filtration and washing with
pentane. Obtained as a white solid (0.73 g, 38 %). 1H NMR (400 MHz, CDCl3):
1-(1-diazo-2,2,2-trifluoroethyl)-4-fluorobenzene (1g)
3
3
δ 7.95 (s, 1H) 7.81 (d, JHH = 8.3 Hz, 2H), 7.32 (m, 4H), 7.13 (d, JHH = 8.3 Hz,
2H), 2.42 (s, 3H), 2.47 (s, 3H). 13C NMR (100 MHz, CDCl3): δ 144.9, 142.1,
141.8 (q, 2JCF = 35.8 Hz), 134.6, 130.7, 129.9, 128.0, 122.1, 119.0 (q, 1JCF = 275
Hz), 21.7, 21.5 (C=N2 not observed). 19F NMR (376 MHz, CDCl3) δ -68.4 (s, 3F).
Data consistent with literature values.33
Prepared following general procedure B from tosylhydrazone 1’g (1.45 g, 4.0
mmol). Purified by silica gel chromatography (pentane) and obtained as a
orange/red liquid (250 mg, 31 %). 1H NMR (400 MHz, CDCl3): δ 7.14-7.06 (m,
1
1
4H). 13C NMR (101 MHz, CDCl3): δ 161.7 (d, JCF = 246.8 Hz), 126.0 (q, JCF
=
269.2 Hz), 124.4 (dq, J = 8.1, 1.4 Hz), 119.4 (d, J = 3.5 Hz), 116.8 (d, J = 22.3
Hz), (C=N2 not observed). 19F NMR (376 MHz, CDCl3): δ -57.6 (s, 3F), -115.9
(s, 1F). IR (neat) υ/ cm-1: 3054, 2080, 1512, 1334, 1306, 1270, 1240, 1167,
1099, 957, 825, 735, 609. HRMS (ESI, negative) calculated for C8H3F4N2- ([M-
H]-): 203.0238, observed: 203.0233.
1-(1-diazo-2,2,2-trifluoroethyl)-4-methylbenzene (1d)
Prepared following general procedure B from tosylhydrazone 1’d (0.72 g, 2.0
mmol), purified by silica gel chromatography (pentane) and obtained as a
1
3
red liquid (169 mg, 42 %). H NMR (400 MHz, CDCl3) δ 6.82 (d, JHH = 8.1 Hz,
1-(1-diazo-2,2,2-trifluoroethyl)-4-(trifluoromethyl)benzene (1h)
2H), 6.75 (d, JHH = 8.1 Hz, 2H), 1.98 (s, 3H). 13C NMR (126 MHz, CDCl3) δ
3
1
2
136.2, 130.7, 126.9 (q, JCF = 270 Hz), 123.1, 120.6, 60.2 (q, JCF = 43.9 Hz),
21.1. 19F NMR (376 MHz, CDCl3) δ -57.5 (s, 3F). Data consistent with
literature values.23
Prepared following general procedure
C from 4’-trifluoromethyl-2,2,2-
trifluoroacetophenone (1.01 g, 4.2 mmol.). Purified by silica gel column
chromatography (pentane) and obtained as a yellow oil (46 mg, 4 % over
two steps). 1H NMR (500 MHz, CDCl3): δ 7.73–7.50 (m, 2H), 7.22–7.07 (m,
2H). 13C NMR (125 MHz, CDCl3): δ 128.3, 128.0 (q, 2JCF = 32.9 Hz), 126.5 (q, J =
1
1
1-bromo-3-(1-diazo-2,2,2-trifluoroethyl)benzene (1e)
3.9 Hz), 125.2 (q, JCF = 269.7 Hz), 124.0 (q, JCF = 271.8 Hz), 122.0 (d, J = 1.0
Hz), (C=N2 not observed). 19F NMR (376 MHz, CDCl3): δ -57.4 (s, 3F), -62.6 (s,
3F). IR (neat) υ/ cm-1: 2931, 2859, 2088, 1619, 1523, 1325, 1280, 1206, 1169,
1110, 1069, 1016, 958, 831, 738.39
Prepared following general procedure
C
from 3’-bromo-2,2,2-
trifluoroacetophenone (2.0 g, 7.9 mmol.). Purified by silica gel column
chromatography (pentane) and obtained as a red oil (120 mg, 6 % over two
steps). 1H NMR (500 MHz, C6D6): 7.02 – 6.88 (m, 2H), 6.55 (t, J = 7.9 Hz, 1H),
6.52 – 6.45 (m, 1H). 13C NMR (125 MHz, C6D6): δ 130.6, 128.7, 125.8, 125.5

6
<Journal Name>
ACCEPTED MANUSCRIPT
2-chloro-4-(1-diazo-2,2,2-trifluoroethyl)-1-fluorobenzene (1i)
2924, 2857, 1359, 1170, 1119, 1070, 999, 811, 684. HRMS (ESI, positive)
calculated for C18H20F3N2O2S+ ([M+H]+): 385.1192, observed: 385.1202.
Prepared following general procedure from the corresponding
C
trifluoroacetophenone (1.0 g, 4.4 mmol). Purified by silica gel column
chromatography (pentane) and obtained as a red oil (14 mg, 2 % over two
1-(1-diazo-2,2,2-trifluoroethyl)-4-propylbenzene (1l)
steps). 1H NMR (400 MHz, CDCl3): δ 7.19 (t, J = 8.6 Hz, 1H), 7.13 (dd, J = 6.4,
1
2.4 Hz, 1H), 6.98-6.94 (m, 1H). 13C NMR (101 MHz, CDCl3): δ 156.6 (d, JCF
=
Prepared following general procedure B from tosylhydrazone 1’l (1.33 g,
3.46 mmol), purified by silica gel chromatography (pentane) and obtained as
a orange/red liquid (194 mg, 25 %). 1H NMR (400 MHz, CDCl3): δ 7.23 (d, 3JHH
1
249.8 Hz), 126.7, 125.6 (q, JCF = 269.4 Hz), 124.6 (d, J = 1.3 Hz), 122.3 (m),
121.1 (d, J = 4.2 Hz), 117.9 (d, J = 22.0 Hz), (C=N2 not observed). 19F NMR
(376 MHz, CDCl3): δ -57.5 (s, 3F), -118.1 (td, J = 7.2, 4.2 Hz, 1F). IR (neat) υ/
cm-1: 2925, 2853, 2237, 2172, 2089, 2011, 1599, 1504, 1466, 1324, 1257,
1194, 1145, 1066, 814, 704, 628, 617.39
3
3
= 8.6 Hz, 2H), 7.03 (d, JHH = 7.9 Hz, 2H), 2.60 (t, JHH = 7.6 Hz, 2H), 1.70-1.61
(m, 2H), 0.96 (t, 3JHH = 7.3 Hz, 3H). 19F NMR (377 MHz, CDCl3): δ -57.4 (s,
3F). 13C NMR (101 MHz, CDCl3): δ 140.9, 129.7, 125.7 (q, JCF = 268.6 Hz),
1
122.5, 120.5, 37.6, 24.6, 13.9, (C=N2 not observed). IR (neat) υ/ cm-1: 2963,
2934, 2874, 2079, 1516, 1345, 1276, 1167, 1145, 1105, 957, 835, 799, 738,
-
4-methyl-N'-(2,2,2-trifluoro-1-(4-
640. HRMS (ESI, negative) calculated for C11H10F3N2 ([M-H]-): 227.0802,
methoxyphenyl)ethylidene)benzenesulfonohydrazide (1’j)
observed: 227.0556.
Prepared following general procedure
A
from 4’-methoxy-2,2,2-
trifluoroacetophenone (4.08 g, 20 mmol.) in methanol (65 °C, 12 h). Purified
4.3 Diazo insertion reaction
by precipitation upon cooling to room temperature and subsequent
1
filtration. Obtained as a pale-yellow solid (2.31 g, 28%). H NMR (400 MHz,
General procedure D: CF3C(Ar)N2 Insertion into nBu3SnH under inert
CD3OD) δ 7.80-7.79 (m, 2H), 7.43 (m, 2H), 7.32-7.30 (m, 2H), 7.09-7.06 (m,
2H), 3.87 (s, 3H), 2.45 (s, 3H), (unable to see N-H). 13C NMR (100 MHz,
atmosphere
2
A flame dried, argon purged vial was charged with aryl 2,2,2-
CD3OD) δ 161.5, 144.1, 141.0 (q, JCF = 38.9 Hz), 135.3, 129.8, 129.2, 127.7,
1
trifluorodiazoethane 1 (1.0 eq., 0.1 mmol), nBu3SnH (26.5 μL, 1.0 eq, 0.1
mmol) and degassed CH2Cl2 (0.7 mL). In a separate flame dried, argon
purged vial was added Rh2(OAc)4 (1.8 mg, 4 mol%, 0.004 mmol) and
degassed CH2Cl2 (0.5 mL). Diazo compound and nBu3SnH solution were
added to the Rh2(OAc)4 suspension over <1 min at room temperature. After
evolution of N2 had stopped and characteristic orange/red colour of diazo
compound had disappeared, the reaction progress was monitored by TLC.
Typically, the reaction was complete in less than 15 minutes. The reaction
mixture was filtered through a short plug of silica gel eluting with CH2Cl2,
evaporated under reduced pressure and the crude product purified by silica
gel column chromatography.
120.4 (q, JCF = 274 Hz), 118.9, 114.2, 54.2, 20.0. 19F NMR (376 MHz, CD3OD)
δ -65.5 (s, 3F). Data consistent with literature values.23
1-(1-diazo-2,2,2-trifluoroethyl)-4-methoxybenzene (1j)
Prepared following general procedure B from tosylhydrazone 1’j (2.0 g, 5.38
mmol.). Purified by basic alumina gel chromatography (hexane) and
1
obtained as a red solid (139 mg, 12 %). H NMR (500 MHz, C6D6) δ 6.75-6.73
(m, 2H), 6.60 (d, 3JHH = 9.0 Hz, 2H), 3.21 (s, 3H). 19F NMR (376 MHz, CDCl3) δ -
57.6 (s, 3F). Data consistent with literature values.37
4-(1-diazo-2,2,2-trifluoroethyl)-2-fluoro-1-methylbenzene (1k)
General procedure E: CF3C(Ar)N2 Insertion into nBu3SnH in an open vial
Prepared following general procedure
C
from the corresponding
To a solution of aryl 2,2,2-trifluorodiazoethane 1 (1.0 eq, 0.1 mmol) and
nBu3SnH (26.5 μL, 1.0 eq, 0.1 mmol) in CH2Cl2 (1.2 mL) in an open vial was
added Rh2(OAc)4 (1.77 mg, 4 mol%, 0.004 mmol). After evolution of N2 had
stopped and characteristic orange/red colour of diazo compound had
disappeared, the reaction progress was monitored by TLC. Typically, the
reaction was complete in less than 15 min. The reaction mixture was filtered
through a short plug of silica gel eluting with CH2Cl2, evaporated under
reduced pressure and the crude product purified by silica gel column
chromatography.
trifluoroacetophenone (1.8 g, 8.7 mmol.). Purified by silica gel column
chromatography (pentane) and obtained as a red oil (47 mg, 2 % over two
1
steps). H NMR (500 MHz, CD2Cl2): δ 7.24 (t, J = 8.2 Hz, 1H), 6.86 – 6.71 (m,
2H), 2.26 (d, 4JHF = 1.9 Hz, 3H). 13C NMR (126 MHz, Methylene Chloride-d2) δ
162.4 (d, J = 244.9 Hz), 133.1 (d, J = 6.1 Hz), 126.2 (q, J = 269.0 Hz), 123.4 (d, J
= 9.1 Hz), 123.2 (d, J = 17.3 Hz), 118.3 (d, J = 3.3 Hz), 109.6 (d, J = 26.2 Hz),
14.4 (C=N2 not observed). 19F NMR (376 MHz, CDCl3): δ -56.0 (s, 3F), -114.3
(m, 1F). IR (neat) υ/ cm-1: 2960, 2933, 2867, 2082, 1629, 1579, 1514, 1354,
1327, 1295, 1273, 1235, 1204, 1104, 1009, 875, 862, 807, 760, 734, 644.
Compound 1k was found to be unstable under various ionisation techniques
and HRMS could therefore not be obtained.
General Procedure F: Asymmetric CF3C(Ar)N2 insertion into nBu3SnH
A
flame dried, argon purged vial was charged with aryl 2,2,2-
trifluorodiazoethane 1 (1.0 eq, 0.1 mmol), nBu3SnH (26.5 μL, 1.0 eq, 0.1
mmol) and degassed CH2Cl2 (0.7 mL). In a separate flame dried, argon
purged vial was added Rh2(S-tertPTTL)4 (1.77 mg, 4 mol%, 0.004 mmol) and
degassed CH2Cl2 (0.5 mL) and the mixture was cooled down to -78 °C. The
diazo compound and nBu3SnH solution were added to the Rh2(S-tertPTTL)4
suspension over <1 min at -78 °C. After evolution of N2 had stopped and
characteristic orange/red colour of diazo compound had disappeared, the
reaction progress was monitored by TLC. Typically, the reaction was
complete in less than 30 min. The reaction mixture was filtered through a
short plug of silica gel eluting with CH2Cl2, evaporated under reduced
pressure and the crude product was purified by silica gel column
chromatography.
4-methyl-N'-(2,2,2-trifluoro-1-(4-
propylphenyl)ethylidene)benzenesulfonohydrazide (1’l)
Prepared following general procedure
A
from 4'-N-propyl-2,2,2-
trifluoroacetophenone (1.0 g, 4.60 mmol.) in methanol (65 oC, 12 h). Purified
by cooling to room temperature and subsequent filtration and washing with
pentane. Obtained as a white solid (1.33 g, 75 %). Used without further
purification. 1H NMR (400 MHz, CDCl3): δ 7.98 (s, 1H), 7.81 (d, J = 8.3 Hz,
2H), 7.36 7.31 (m, 4H), 7.14 (d, J = 8.0 Hz, 2H), 2.63 (t, 3JHH = 7.7 Hz, 2H), 2.46
(s, 3H), 1.71, 1.62 (m, 2H), 0.97 (t, JHH = 7.3 Hz, 3H). 13C NMR (126 MHz,
3
2
CDCl3): δ 146.9, 145.0, 142.0 (q, JCF = 35.6 Hz), 134.7, 130.2, 130.0, 128.1,
1
122.5, 120.1 (q, JCF = 274.9 Hz), 77.2, 38.1, 24.3, 21.8, 14.0. 19F NMR (377
MHz, CDCl3): δ -68.3 (s, 3F). MP 108-109 oC. IR (neat) υ/ cm-1: 3171, 2964,

+
(1-([1,1'-biphenyl]-4-yl)-2,2,2-trifluoroethyl)tributylstannane (2a)
HRMS (CI) calculated for C9H8F2 ([M-nBu3SnF]+): 154.0594, observed:
ACCEPTED MANUSCRIPT
154.0585; calculated for C12H27Sn+ ([nBu3Sn]+): 291.1129, observed:
Prepared following general procedure D. Purified by silica gel column
chromatography (pentane) and obtained as a colourless oil (39 mg, 74 %). 1H
291.1129.38
NMR (400 MHz, CDCl3): δ 7.60-7.58 (m, 2H), 7.53 (d, J = 8.4 Hz, 2H), 7.44 (t, J
3
= 7.6 Hz, 2H), 7.34 (t, J = 7.4 Hz, 1H), 7.22 (d, J = 8.2 Hz, 2H), 3.23 (q, JHF
=
(1-(3-bromophenyl)-2,2,2-trifluoroethyl)tributylstannane (2e)
3
13.7 Hz, 1H), 1.47-1.39 (m, 6H), 1.28 (m, 6H), 0.97 (m, 6H), 0.87 (t, JHH = 7.3
Hz, 9H). 13C NMR (101 MHz, CDCl3): δ 140.9, 138.7, 135.8 (q, J = 3.8 Hz),
Prepared following general procedure D. Purified by silica gel column
chromatography (pentane) and obtained as a colourless oil (31 mg, 59 %). 1H
NMR (500 MHz, CDCl3): δ 7.31-7.29 (m, 2H), 7.15 (t, J = 8.1 Hz, 1H), 7.07 (d, J
1
129.7 (q, JCF = 274.3 Hz), 128.9, 128.3, 127.5, 127.3, 127.0, 38.9 (q, 2JCF =
3
30.9 Hz), 28.8, 27.4, 13.7, 10.6. 19F NMR (376 MHz, CDCl3): δ -55.7 (d, JFH
=
13.6 Hz, 3F). IR (neat) υ/ cm-1: 3031, 2956, 2923, 2872, 2854, 1907, 1729,
1612, 1600, 1519, 1488, 1463, 1416, 1377, 1345, 1306, 1281, 1261, 1238,
1204, 1123, 1101, 1075, 1039, 1008, 960, 912, 878, 848, 823, 764, 740, 727,
3
= 7.9 Hz, 1H), 3.12 (q, JHF = 13.5 Hz, 1H), 1.45-1.34 (m, 6H), 1.27 (m, 6H),
3
1.01-0.90 (m, 6H), 0.87 (t, JHH = 7.3 Hz, 9H). 13C NMR (126 MHz, CDCl3): δ
1
139.3-139.1 (m), 130.7, 130.3, 129.3 (q, JCF = 275.0 Hz), 128.9, 126.3, 122.9,
695, 668, 614. HRMS (CI) calculated for C14H10F2 ([M-nBu3SnF]+): 216.0751,
+
2
38.9 (q, JCF = 31.2 Hz), 28.7, 27.4, 13.7, 10.6. 19F NMR (377 MHz, CDCl3): δ -
observed: 216.0753; calculated for C12H27Sn+ ([nBu3Sn]+): 291.1129,
observed: 291.1145.38 Asymmetric reaction was performed using general
procedure F. The product (+)-(2a) was obtained in 57 % yield with this
procedure. 94 % ee, HPLC conditions; Chiralpak IA column, hexane = 100%,
flow rate = 1.0 mL/min, 25 °C, wavelength = 254 nm, tR = 5.89 min for minor
isomer, tR = 6.72 min for major isomer: [α]D25 = +55.7 (c 1.46, MeOH).
3
55.7 (d, JFH = 13.4 Hz, 3F). IR (neat) υ/ cm-1: 2957, 2923, 2872, 2854, 1593,
1563, 1475, 1378, 1341, 1239, 1195, 1128, 1088, 1039, 996, 877, 779, 713,
692, 620. HRMS (CI) calculated for C12H27Sn+ ([nBu3Sn]+): 291.1129, observed:
291.1132.38
tributyl(2,2,2-trifluoro-1-phenylethyl)stannane (2f)
Prepared following general procedure D. Purified by silica gel column
chromatography (pentane) and obtained as a colourless oil (22 mg, 49 %). 1H
(1-(4-bromophenyl)-2,2,2-trifluoroethyl)tributylstannane (2b)
3
Prepared following general procedure E. Purified by silica gel column
chromatography (pentane) and obtained as a colourless oil (34 mg, 64 %). 1H
NMR (400 MHz, CDCl3): δ 7.40 (d, J = 8.6 Hz, 2H), 7.01 (d, J = 8.4 Hz, 2H),
NMR (500 MHz, CDCl3): δ 7.26 (s, 2H), 7.17-7.13 (m, 3H), 3.16 (q, JHF = 13.7
Hz, 1H), 1.43-1.36 (m, 6H), 1.26 (m, 6H), 0.97-0.90 (m, 6H), 0.86 (t, 3JHH = 7.3
1
Hz, 9H). 13C NMR (126 MHz, CDCl3): δ 136.6 (q, J = 3.9 Hz), 129.7 (q, JCF
=
3
2
3.12 (q, JHF = 13.6 Hz, 1H), 1.45-1.37 (m, 6H), 1.29-1.24 (m, 6H), 0.99-0.90
274.9 Hz), 128.8, 127.9, 125.8, 39.2 (q, JCF = 30.9 Hz), 28.7, 27.4, 13.7, 10.5.
(m, 6H), 0.87 (t, 3JHH = 7.3 Hz, 9H). 13C NMR (101 MHz, CDCl3): δ 135.9, 131.9,
3
19F NMR (377 MHz, CDCl3): δ -55.8 (d, JFH = 13.5 Hz, 3F). IR (neat) υ/ cm-1:
1
2
130.7 (q, JCF = 275.0 Hz), 129.5, 119.6, 38.7 (q, JCF = 31.2 Hz), 28.7, 27.4,
13.7, 10.5. 19F NMR (376 MHz, CDCl3): δ -55.9 (d, 3JFH = 13.5 Hz, 3F). IR (neat)
υ/ cm-1: 2957, 2924, 2872, 2854, 1895, 1731, 1592, 1490, 1463, 1412, 1377,
1350, 1339, 1301, 1264, 1238, 1196, 1127, 1100, 1076, 1039, 1011, 960,
941, 875, 843, 809, 769, 747, 721, 691, 671, 649. HRMS (CI) calculated for
C12H27Sn+ ([nBu3Sn]+): 291.1129, observed: 291.1138.38
2957, 2924, 2872, 2854, 1601, 1495, 1456, 1356, 1277, 1240, 1203, 1125,
+
1074, 1034, 874, 757, 698, 671, 615. HRMS (CI) calculated for C8H6F2 ([M-
nBu3SnF]+): 140.0438 observed: 140.0426; calculated for C12H27Sn+
([nBu3Sn]+): 291.1129, observed: 291.1135.38
tributyl(2,2,2-trifluoro-1-(4-fluorophenyl)ethyl)stannane (2g)
Prepared following general procedure D. Purified by silica gel column
chromatography (pentane) and obtained as a colourless oil (25 mg, 54 %). 1H
NMR (500 MHz, CDCl3): δ 7.10 (dd, J = 8.4, 5.4 Hz, 2H), 6.98 (t, J = 8.7 Hz,
methyl 4-(2,2,2-trifluoro-1-(tributylstannyl)ethyl)benzoate (2c)
Prepared following general procedure E. Purified by silica gel column
chromatography (100% pentane to pentane/CH2Cl2 1:1) and obtained as a
3
2H), 3.13 (q, JHF = 13.6 Hz, 1H), 1.46-1.34 (m, 6H), 1.26 (m, 6H), 1.00-0.89
1
3
(m, 6H), 0.86 (t, 3JHH = 7.3 Hz, 9H). 13C NMR (126 MHz, CDCl3): δ 161.2 (d, 1JCF
colourless oil (31 mg, 61 %). H NMR (400 MHz, CDCl3): δ 7.95 (d, JHH = 8.5
3
3
1
Hz, 2H), 7.19 (d, JHH = 8.3 Hz, 2H), 3.90 (s, 3H), 3.25 (q, JHF = 13.5 Hz, 1H),
1.45-1.31 (m, 6H), 1.25 (m, 6H), 1.01-0.89 (m, 6H), 0.85 (t, 3JHH = 7.3 Hz, 9H).
13C NMR (126 MHz, CDCl3): δ 167.0, 142.5 (q, J = 4.0 Hz), 130.2, 129.3 (q, 1JCF
= 244.5 Hz), 132.4 (q, J = 3.9 Hz), 129.5 (q, JCF = 274.9 Hz), 129.5 (q, J = 7.8
2
Hz), 115.6 (d, J = 21.3 Hz), 38.3 (q, JCF = 31.2 Hz), 28.7, 27.4, 13.7, 10.5. 19F
NMR (471 MHz, CDCl3): δ -56.4 (d, 3JFH = 3.6 Hz, 3F), -117.3 (m, 1F). IR (neat)
υ/ cm-1: 2958, 2924, 2873, 2855, 1607, 1509, 1464, 1420, 1342, 1272, 1246,
1228, 1200, 1161, 1117, 1094, 1042, 961, 876, 825, 791, 721, 664. HRMS (CI)
2
= 275.0 Hz), 127.5, 127.4, 52.2, 39.7 (q, JCF = 31.2 Hz), 28.7, 27.4, 13.7, 10.6.
3
19F NMR (377 MHz, CDCl3): δ -55.3 (d, JFH = 13.2 Hz, 3F). IR (neat) υ/ cm-1:
+
calculated for C8H5F3 ([M-nBu3SnF]+): 158.0343 observed: 158.0330;
2956, 2925, 2873, 2855, 1724, 1610, 1436, 1348, 1275, 1239, 1184, 1112,
1021, 962, 860, 771, 711. HRMS (CI) calculated for C22H36F3O2Sn+ ([M+H]+):
509.1689, observed: 509.1677. Asymmetric reaction was performed using
general procedure F. The product (+)-(2c) was obtained in 77 % yield with
this procedure. 84 % ee, HPLC conditions; Chiralpak IA column, hexane =
100%, flow rate = 1.0 mL/min, 25 °C, wavelength = 254 nm, tR = 10.50 min
calculated for C12H27Sn+ ([nBu3Sn]+): 291.1129, observed: 291.1133.38
tributyl(2,2,2-trifluoro-1-(4-(trifluoromethyl)phenyl)ethyl)stannane (2h)
for major isomer, tR = 12.13 min for minor isomer: [α]D = + 1.0 (c 1.26,
Prepared following general procedure D. Purified by silica gel column
chromatography (pentane) and obtained as a colourless oil (32 mg, 62 %). 1H
NMR (400 MHz, CDCl3): δ 7.54 (d, J = 8.1 Hz, 2H), 7.24 (d, J = 8.2 Hz, 2H), 3.24
25
MeOH).
3
(q, JHF = 13.4 Hz, 1H), 1.49–1.32 (m, 6H), 1.32–1.16 (m, 6H), 1.02–0.90 (m,
3
6H), 0.86 (t, JHH = 7.3 Hz, 9H). 13C NMR (101 MHz, CDCl3): δ 141.0, 129.1 (q,
tributyl(2,2,2-trifluoro-1-(p-tolyl)ethyl)stannane (2d)
1JCF = 271.8 Hz), 127.8 (q, 2JCF = 32.7 Hz), 127.6 (t, J = 1.4 Hz), 125.6 (q, J = 3.5
1
2
Prepared following general procedure D. Purified by silica gel column
chromatography (pentane) and obtained as a colourless oil (30 mg, 65 %). 1H
NMR (500 MHz, CDCl3): δ 7.08 (d, J = 8.0 Hz, 2H), 7.03 (d, J = 8.1 Hz, 2H),
3.12 (q, 3JHF = 13.8 Hz, 1H), 2.31 (s, 3H), 1.47-1.32 (m, 6H), 1.26 (m, 6H), 0.99-
Hz), 124.2 (q, JCF = 271.8 Hz), 39.2 (q, JCF = 31.3 Hz), 28.5, 27.2, 13.5, 10.4.
3
19F NMR (376 MHz, CDCl3): δ -55.5 (d, JFH = 13.4 Hz, 3F), -62.4 (3F). IR (neat)
υ/ cm-1: 2959, 2925, 2874, 2856, 1620, 1582, 1519, 1464, 1423, 1378, 1326,
1286, 1240, 1202, 1166, 1121, 1103, 1069, 1019, 960, 909, 879, 849, 825,
767, 742, 690, 671. HRMS (CI) calculated for C12H27Sn+ ([nBu3Sn]+): 291.1129,
observed: 291.1129.38
3
0.90 (m, 6H), 0.86 (t, JHH = 7.3 Hz, 9H). 13C NMR (126 MHz, CDCl3): δ 135.4,
1
2
133.4 (q, J = 3.9 Hz), 129.7 (q, JCF = 275.0 Hz), 129.5, 127.9, 38.7 (q, JCF
=
30.8 Hz), 28.8, 27.4, 21.1, 13.7, 10.4. 19F NMR (376 MHz, CDCl3): δ -56.0 (d,
3JFH = 13.7 Hz, 3F). IR (neat) υ/ cm-1: 2957, 2923, 2872, 2855, 1513, 1463,
1342, 1309, 1241, 1199, 1123, 1103, 1074, 1042, 876, 808, 719.43, 665.

8
<Journal Name>
ACCEPTED MANUSCRIPT
HRMS (CI) calculated for C11H12F2 ([M-nBu3SnF]+): 182.0907, observed:
+
tributyl(1-(3-chloro-4-fluorophenyl)-2,2,2-trifluoroethyl)stannane (2i)
182.0905; calculated for C12H27Sn+ ([nBu3Sn]+): 291.1129, observed:
291.1136.38
Prepared following general procedure D, on 0.05mmol scale. Purified by
silica gel column chromatography (pentane) and obtained as a colourless oil
(13 mg, 52 %). 1H NMR (500 MHz, CDCl3): δ 7.17 (dd, J = 6.9, 2.3 Hz, 1H),
3
7.06 (t, J = 8.7 Hz, 1H), 7.00-6.97 (m, 1H), 3.09 (q, JHF = 13.4 Hz, 1H), 1.44-
(1-([1,1'-biphenyl]-4-yl)-2,2,2-trifluoroethyl)dimethyl(phenyl)silane (2m)
1.38 (m, 6H), 1.30-1.23 (m, 6H), 0.99-0.92 (m, 6H), 0.87 (t, 1JHH = 7.3 Hz, 9H).
13C NMR (126 MHz, CDCl3): δ 156.5 (d, JCF = 247.8 Hz), 134.1-133.8 (m),
1
Prepared following general procedure D, with substitution of nBu3SnH for
PhMe2SiH (15.3 μL, 1.0 eq, 0.1 mmol). Purified by silica gel column
chromatography (5-15% CH2Cl2 in pentane) and obtained as a white solid in
92% yield (34 mg, 0.09 mmol). 1H NMR (400 MHz, CDCl3) δ 7.58 (d, J = 7.3 Hz,
2H), 7.49-7.41 (m, 4H), 7.40-7.30 (m, 6H), 7.06 (d, J = 8.1 Hz, 2H), 3.16 (q, J =
12.9 Hz, 1H), 0.48 (s, 3H), 0.40 (s, 3H). 13C NMR (126 MHz, CDCl3) δ 140.7,
139.5, 135.3, 134.3, 132.9 (q, J = 3.2 Hz), 129.8, 129.5, 128.9, 128.3 (q, J =
1
129.8, 129.3 (q, JCF = 275.0 Hz), 127.5 (d, J = 7.0 Hz), 121.2 (d, J = 17.9 Hz),
116.8 (d, J = 21.0 Hz), 38.2 (q, JCF = 31.5 Hz), 28.7, 27.4, 13.7, 10.6. 19F NMR
2
3
(377 MHz, CDCl3): δ -56.2 (d, JFH = 13.2 Hz, 3F), -119.6- (m, 1F). IR (neat) υ/
cm-1: 2958, 2924, 2855, 1499, 1236, 1230, 1109. HRMS (CI) calculated for
C8H4ClF3 ([M-nBu3SnF]+): 191.9954 observed: 191.9974; calculated for
+
C12H27Sn+ ([nBu3Sn]+): 291.1129, observed: 291.1146.38
277.7 Hz, CF3), 127.9, 127.4, 127.1, 127.1, 43.8 (q, J = 27.7 Hz), -3.4, -3.5. 19
F
NMR (376 MHz, CDCl3) δ -56.5 (t, J = 13.0 Hz, 3F). IR (neat) υ/ cm-1 3071,
3031, 2963, 2905, 2362, 2284, 1488, 1239, 1151, 1133, 1068, 810, 764, 739,
695, 649. HRMS (EI) calculated for C22H21F3Si+ (M+): 370.1359, observed:
370.1363. The asymmetric reaction was performed using general procedure
F, with substitution of nBu3SnH for PhMe2SiH (15.3 μL, 1.0 eq, 0.1 mmol).
Purified by silica gel column chromatography (5-15% CH2Cl2 in pentane). The
product (+)-(2m) was obtained in 65 % and 99 % ee, HPLC conditions;
Chiralcel OJ-H column, hexane/iPrOH = 99:1, flow rate = 1.0 mL/min, 25 °C,
wavelength = 250 nm, tR = 15.06 min for major isomer, tR = 20.53 min for
minor isomer: [α]D25 = + 75.8 (c 0.85, MeOH).
tributyl(2,2,2-trifluoro-1-(4-methoxyphenyl)ethyl)stannane (2j)
Prepared following general procedure D. Purified by preparative TLC (5%
1
EtOAc in cyclohexane) and obtained as a colourless oil (18.3 mg, 38 %). H
NMR (500 MHz, CDCl3): δ 7.11–7.02 (m, 2H), 6.87–6.79 (m, 2H), 3.79 (s, 3H),
3
3.09 (q, JHF = 13.8 Hz, 1H), 1.49 1.30 (m, 6H), 1.26 (h, J = 7.3 Hz, 6H), 1.02–
3
0.87 (m, 6H), 0.86 (t, JHH = 7.3 Hz, 9H). 13C NMR (125 MHz, CDCl3): δ 157.9,
129.8 (q, 1JCF = 274.9 Hz), 129.3, 128.5 (q, J = 4.2 Hz), 114.2, 55.4, 38.1 (q, 2JCF
= 30.9 Hz), 28.8, 27.4, 13.7, 10.4. 19F NMR (376 MHz, CDCl3): δ -56.5 (d, 3JFH
=
13.6 Hz, 3F). IR (neat) υ/ cm-1: 2956, 2924, 2872, 2854, 1612, 1581, 1511,
1464, 1443, 1423, 1377, 1351, 1307, 1283, 1250, 1235, 1202, 1180, 1122,
1100, 1075, 1038, 961, 931, 875, 849, 821, 775, 747, 726, 687, 665. HRMS
(CI) calculated for C9H8F2O+ ([M-nBu3SnF]+): 170.0543, observed: 170.0520;
calculated for C12H27Sn+ ([nBu3Sn]+): 291.1129, observed: 291.1116.38
Asymmetric reaction was performed using general procedure F. The product
(-)-(2j) was obtained in 57 % yield with this procedure. 85 % ee, HPLC
conditions; Chiralpak IC column, hexane = 100%, flow rate = 1.0 mL/min, 25
°C, wavelength = 254 nm, tR = 9.20 min for major isomer, tR = 10.11 min for
minor isomer: [α]D25 = -0.6 (c 0.46, MeOH).
(1-([1,1'-biphenyl]-4-yl)-2,2,2-trifluoroethyl)tributylgermane (2n)
Prepared following general procedure D, with substitution of nBu3SnH for
nBu3GeH (25.8 μL, 1.0 eq, 0.1 mmol). Purified by silica gel column
chromatography (pentane) and obtained as a colourless oil in 58% yield (28
mg, 0.06 mmol). 1H NMR (400 MHz, CDCl3): δ 7.61-7.58 (m, 2H), 7.56-7.53
(m, 2H), 7.47-7.42 (m, 2H), 7.37-7.33 (m, 1H), 7.25 (d, J = 7.7 Hz, 2H), 3.15 (q,
3JHF = 13.2 Hz, 1H), 1.34-1.24 (m, 12H), 0.92-0.83 (m, 15H). 13C NMR (101
1
MHz, CDCl3): δ 140.8, 139.3, 134.3, 129.0, 128.9 (q, JCF = 276.8 Hz), 128.9,
2
127.4, 127.3, 127.1, 41.0 (q, JCF = 28.8 Hz), 27.0, 26.6, 13.8, 12.7. 19F NMR
tributyl(2,2,2-trifluoro-1-(3-fluoro-4-methylphenyl)ethyl)stannane (2k)
(377 MHz, CDCl3): δ -57.1 (d, 3JFH = 13.2 Hz, 3F). IR (neat) υ/ cm-1: 3032, 2956,
2927, 2871, 2857, 1910, 1600, 1520, 1488, 1464, 1416, 1378, 1344, 1306,
1281, 1262, 1242, 1205, 1141, 1131, 1109, 1063, 1008, 964, 912, 884, 855,
826, 765, 743, 729, 695, 681, 654, 616. HRMS (CI) calculated for
C26H41F3GeN+ ([M+NH4]+): 498.2397, observed: 498.2435. The asymmetric
reaction was performed using general procedure F, with substitution of
nBu3SnH for nBu3GeH (25.8 μL, 1.0 eq, 0.1 mmol). The product (+)-(2n) was
obtained in 99 % yield with this procedure. 99 % ee, HPLC conditions;
Chiralpak IC column, hexane = 100%, flow rate = 1.0 mL/min, 25 °C,
wavelength = 254 nm, tR = 6.15 min for major isomer, tR = 6.97 min for
minor isomer: [α]D25 = +54.3 (c 3.46, MeOH).
Prepared following general procedure D. Purified by silica gel column
chromatography (pentane) and obtained as a colourless oil (14.5 mg, 60 %).
1H NMR (500 MHz, CDCl3): δ 7.13–7.02 (m, 1H), 6.88–6.74 (m, 2H), 3.11 (q,
3JHF = 13.6 Hz, 1H), 2.23 (d, J = 1.9 Hz, 3H), 1.50–1.34 (m, 6H), 1.34–1.13 (m,
6H), 1.04–0.89 (m, 6H), 0.86 (t, 3JHH = 7.2 Hz, 9H). 13C NMR (125 MHz, CDCl3):
1
δ 161.4 (d, JCF = 244.6 Hz), 136.2 (dd, J = 7.8, 3.9 Hz), 131.7 (d, J = 5.8 Hz),
129.5 (q, 1JCF = 274.8 Hz), 123.3 (d, J = 3.1 Hz), 122.1 (d, J = 17.2 Hz), 114.4 (d,
J = 23.2 Hz), 39.2–38.2 (m), 28.7, 27.4, 14.3 (d, J = 3.3 Hz), 13.7, 10.5. 19F
3
NMR (376 MHz, CDCl3): δ -56.0 (d, JFH = 13.5 Hz, 3F), -117.2 (ddd, J = 10.6,
8.4, 2.2 Hz, 1F). IR (neat) υ/ cm-1: 2957, 2925, 2873, 2855, 627, 1579, 1510,
1463, 1425, 1378, 1340, 1290, 1272, 1238, 1207, 1150, 1128, 1075, 1041,
+
Acknowledgments
999, 958, 876, 851, 817, 787, 755, 710, 683. HRMS (CI) calculated for C9H7F3
([M-nBu3SnF]+): 172.0500, observed: 173.0472; calculated for C12H27Sn+
([nBu3Sn]+): 291.1129, observed: 291.1122.38
Financial support was provided by the EPSRC (S.H.), a CASE Studentship with
AstraZeneca (S.H.), the Swiss National Foundation (J.V.), and the EPSRC
Centre for Doctoral Training in Synthesis for Biology and Medicine
(EP/L015838/1) (D. M. H. A. and R. S.).
tributyl(2,2,2-trifluoro-1-(4-propylphenyl)ethyl)stannane (2l)
Prepared following general procedure D. Purified by silica gel column
chromatography (pentane) and obtained as a colourless oil (25 mg, 51 %). 1H
NMR (500 MHz, CDCl3): δ 7.08 (d, J = 8.2 Hz, 2H), 7.04 (d, J = 8.2 Hz, 2H),
3.13 (q, 3JHF = 13.8 Hz, 1H), 2.55 (t, J = 7.6 Hz, 2H), 1.62 (m, 2H), 1.45-1.31 (m,
References and notes
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39