Synthesis of thiocarbamoyl fluorides and isothiocyanates using CF3SiMe3 and elemental sulfur or AgSCF3 and KBr with amines

Article abstract of DOI:10.1021/acs.orglett.9b00383

Reactions of thiocarbonyl fluoride derived from cheap, readily available, and widely used CF₃SiMe₃, elemental sulfur, and KF with secondary amines and primary amines at room temperature in THF provided a wide variety of thiocarbamoyl fluorides and isothiocyanates in moderate to excellent yields, respectively. The two reactions show broad substrate scope and good functional group tolerance. Moreover, AgSCF₃ reacts with secondary/primary amines under KBr at room temperature, affording quantitative thiocarbamoyl fluorides/isothiocyanates, which feature late-stage application.

Full text of DOI:10.1021/acs.orglett.9b00383

Letter
pubs.acs.org/OrgLett
Cite This: Org. Lett. XXXX, XXX, XXX−XXX
Synthesis of Thiocarbamoyl Fluorides and Isothiocyanates Using
CF3SiMe3 and Elemental Sulfur or AgSCF3 and KBr with Amines
Long Zhen,† Hui Fan,† Xiaoji Wang,‡ and Liqin Jiang*,†
†School of Chemistry and Molecular Engineering, East China Normal University, 500 Dongchuan Road, Shanghai 200241, China
‡School of life Science, Jiangxi Science and Technology Normal University, Nanchang, 330013, China
S
* Supporting Information
ABSTRACT: Reactions of thiocarbonyl fluoride derived from
cheap, readily available, and widely used CF3SiMe3, elemental
sulfur, and KF with secondary amines and primary amines at
room temperature in THF provided a wide variety of
thiocarbamoyl fluorides and isothiocyanates in moderate to
excellent yields, respectively. The two reactions show broad
substrate scope and good functional group tolerance. More-
over, AgSCF3 reacts with secondary/primary amines under
KBr at room temperature, affording quantitative thiocarbamoyl
fluorides/isothiocyanates, which feature late-stage application.
hiocarbamoyl chlorides are well-known1 and have been
Scheme 1. Methods for Thiocarbamoyl Fluorides/
Isothiocyanates through Safe Reagents
2
Tused for the syntheses of biologically active compounds.
However, preparation of thiocarbamoyl chlorides requires the
use of toxic reagents such as thiophosgene3 or Cl2 gas.4
Moreover, the strong electrophilicity of thiocarbamoyl
chlorides limits their late-stage applications. Their fluoride
equivalents should have advantages of better functional group
tolerance and higher chemoselectivity on polyfunctional
molecules due to their lower electrophilicity. In addition,
nitrogen, sulfur, and fluorine elements are very important in
pharmaceuticals,5 all of which are contained in the structures of
thiocarbamoyl fluorides. However, thiocarbamoyl fluorides
received little attention before 2017 due to the lack of safe and
efficient processes to access them.6 Developing methods for
synthesizing thiocarbamoyl fluorides from readily available,
safe, and cheap starting materials would enable their use as
practical and available building blocks. Isothiocyanates are
important building blocks which have been ubiquitously used
in organic synthesis, materials science, biological, and
pharmaceutical fields,7 and many isothiocyanates themselves
show significant biological activities.8 Traditional methods for
preparation of isothiocyanates involve highly toxic and/or
highly electrophilic reagents such as thiophosgene,9 CS2,10
phosgene,11 thiocarbonyldiimidazole,12 or dipyridylthionocar-
bonate (DPT).13 Safety, functional group tolerance, and
selectivity issues still need to be addressed.
the above-reported one-pot, two-step process for trifluorome-
thylation of amines (Scheme 1a,b, previous work 1, 2).14a−c
However, some problems and challenges still exist. (Me4N)-
SCF3 was prepared from CF3SiMe3, elemental sulfur, and
hydrophilic Me4NF.15 Although (Me4N)SCF3 is stable, the
preparation of (Me4N)SCF3 requires very careful and inert
conditions, and preparation without a glovebox often fails due
In 2017, several safe reagents were reported to prepare
trifluoromethylated amines and/or isothiocyanates from
secondary amines and/or primary amines.14 These reagents
include bench-stable solid reagent (Me4N)SCF3 (Scheme
1a,,b, previous work 1),14a,b Ph3P+CF2CO2− (PDFA) and
elemental sulfur (Scheme 1a,b, previous work 2),14c and
Langlois reagent (F3CSO2Na) (Scheme 1b, previous work
3).14d Thiocarbamoyl fluorides are formed as intermediates in
Received: January 29, 2019
© XXXX American Chemical Society
A
DOI: 10.1021/acs.orglett.9b00383
Org. Lett. XXXX, XXX, XXX−XXX

Organic Letters
Letter
to the extremely hygroscopic nature of Me4NF.
Ph3P+CF2CO2− (PDFA) reagent is relatively expensive to
buy, especially on a mole basis. Several groups have reported
the preparation of PDFA from hygroscopic potassium
bromodifluoroacetate.16 In addition, although F3CSO2Na is
cheap, reaction with it to achieve isothiocyanates requires high
temperature (110 °C) and long reaction times (16 h), and the
reaction suffers from a relatively narrow substrate scope and
low functional group tolerance (e.g., pyridinyl and terminal
alkynyl groups are not tolerated).14d The use of readily
available and cheap reagents to prepare thiocarbamoyl
fluorides and/or isothiocyanates with broad substrate scope
and good functional tolerance under mild conditions is in high
demand. Ruppert−Prakash reagent (CF3SiMe3) is a stable,
readily available, easy to handle, relatively cheap, and widely
used reagent.17 CF3SiMe3, S8, and a base have been used for
trifluoromethylthiolation.18 To the best of our knowledge,
although transformations involving in situ generated thio-
carbonyl fluoride (SCF2) have made rapid progress in recent
years,14c,d,19 the use of CF3SiMe3, elemental sulfur, and KF to
generate thiocarbonyl fluoride (SCF2) in situ for useful
transformations has never been reported. Herein, we reported
that reactions of thiocarbonyl fluoride derived from readily
available and cheap CF3SiMe3 and elemental sulfur and KF
with secondary amines/primary amines with THF as solvent at
room temperature provided a wide variety of thiocarbamoyl
fluorides/isothiocyanates in moderate to excellent yields. In
addition, AgSCF3 reacts with secondary/primary amines in the
presence of KBr in CH3CN at room temperature, providing
thiocarbamoyl fluorides/isothiocyanates in almost quantitative
yields, which feature late-stage application (Scheme 1a,b, this
work).
Scheme 2. Substrate Scope for the Reaction of CF3SiMe3,
Elemental Sulfur, and KF with Secondary Amines as Well as
the Reaction of AgSCF3 and KBr with Secondary Amines
a g
,
We began our optimization studies with the reaction of 0.15
mmol of N-methylaniline 1a, 6.0 equiv of S8, 5.0 equiv of
CF3SiMe3, and 3.0 equiv of KF in DMF at room temperature.
Under these conditions, the desired methyl(phenyl)-
carbamothioic fluoride 2a was obtained in 50% yield. After
the bases, solvent, and equivalents of the starting materials
were screened (details in the Supporting Information (SI)), it
was found that the solvent THF plays a key role in the
formation of 2a in high yield. The identified optimized
conditions were 1 mmol of N-methylaniline 1a, 4.0 equiv of S8,
5.0 equiv of CF3SiMe3, and 3.0 equiv of KF in THF at room
temperature under N2, affording 2a in 92% yield (Scheme 2).
In addition, ClCF2CO2Na19f and S8 were also used in the
reaction with 1a in THF or DMF at rt or 80 °C. The best yield
of 2a was only 39% (SI).
With the optimized conditions in hand, we investigated the
substrate scope of the reaction of CF3SiMe3, elemental sulfur,
KF, and secondary amines (Scheme 2). N-Aryl-N-alkylamines
were first investigated. Aryl groups containing ortho-, meta-,
and para-electron-donating or electron-neutral substituents
afforded the desired thiocarbamoyl fluorides products 2a−i in
excellent yields in 1 h. In particular, tertiary amine was
tolerated (2h). N1,N4-Dimethylbenzene-1,4-diamine reacted
selectively at one secondary amine, and the other was
preserved (2i). N-Methyl-[1,1′-biphenyl]-4-amine (1j) and
N-methylnaphthalen-2-amine (1k) also gave the desired 2j and
2k in good yields, respectively. When aryls bore electron-
withdrawing substituents, the corresponding N-aryl-N-alkyl-
amines were found to require 8.0 equiv of CF3SiMe3 (details in
the SI) at otherwise identical conditions to furnish various
corresponding thiocarbamoyl fluorides in moderate to good
a
Conditions 1: 1.0 mmol of 1, 5.0 mmol of CF3SiMe3, 4.0 mmol of
elemental sulfur, and 3.0 mmol of KF in 20 mL of THF at room
B
DOI: 10.1021/acs.orglett.9b00383
Org. Lett. XXXX, XXX, XXX−XXX

Organic Letters
Letter
Scheme 2. continued
Scheme 3. Substrate Scope for the Reaction of CF3SiMe3,
Elemental Sulfur, and KF with Primary Amines as Well as
the Reaction of AgSCF3 and KBr with Primary Amines
a f
,
b
c
temperature reacted for 1 h under N2. 10 mmol scale. Conditions 2:
0.2 mmol of 1, 0.3 mmol of AgSCF3, and 0.3 mmol of KBr in 4 mL of
d
CH3CN at room temperature reacted for 1 h. 8.0 mmol of
e
f
g
CF3SiMe3. 12 h. 1 mmol scale. Isolated yield (the yields in
parentheses with blue color and the yield of 2ao, 2ap were obtained
under conditions 2; other yields were obtained under conditions 1).
yields (2l−v). Fluoro, chloro, bromo, trifluoromethyl, nitro,
cyano, and ester functional groups were all tolerated.
Compound 1v containing carboxylic acid functionality also
gave the desired 2v, albeit in low yield. In addition,
heterocycles such as pyridine (2w) and thiophene (2x) were
also compatible. Indoline (1y) performed well. The alkenyl
group was also tolerated (2z). N-Benzyl-4-chloroaniline (1aa)
and N-hexyl-4-chloroaniline (1ab) gave higher yields than N-
methyl-4-chloroaniline (1l).
Next, N,N-dialkylamines were investigated and consistently
gave the corresponding thiocarbonyl fluoride products in good
yields under the optimized conditions (2ac−ao) in addition to
2ai. Compound 2ai is volatile, leading to a decreased isolated
yield. In particular, a series of heterocycles including
pyrrolidine (1ak), piperidine (1al), morpholine (1am), and
thiomorpholine (1an) were smoothly converted to the
corresponding thiocarbamoyl fluoride products 2ak−an,
which could be used in the biological and medicinal fields.
Piperazine (1ao) reacted at both of the secondary amine
positions, resulting in 2ao in 88% yield. On a 10 mmol scale of
1a, the reaction also proceeds readily to afford 2a (1.52 g, 9.0
mmol) in 90% yield.
Recently, we reported that AgSCF3 reacts with propargyl-
amines in the presence of KBr in CH3CN to give access to
allenyl thiocyanates via propargyl isothiocyanate intermediates
that undergo a [3,3]-sigmatropic rearrangement.19e However,
the reaction of secondary amines with thiocarbonyl fluoride
derived from AgSCF3 have never been reported. We found that
electron-donating (1c,k) or electro-withdrawing (1l,n,o,r−v)
substituted N-aryl-N-alkylamines, N-(pyridin-2-yl)-N-methyl-
amine (1w), or N,N-dialkylamines (1ac, 1an) react with
AgSCF3 under KBr in CH3CN at room temperature,
consistently affording the corresponding thiocarbamoyl fluo-
rides (2c,k,l,n,o,r−w, 2ac, 2an) in quantitative yields. More-
over, this methodology could be employed in late-stage
pharmaceutical modification. The tetracaine analogue 2ap
and amoxapine analogue 2aq were obtained in excellent yields
through this transformation, leaving the other sensitive
nucleophilic moieties (such as tertiary amine, imine)
completely untouched (Scheme 2).
The success of the reaction of secondary amines with
CF3SiMe3, S8, and KF prompted us to investigate the reaction
of thiocarbonyl fluoride from CF3SiMe3, S8, and KF with
primary amines for preparation of isothiocyanates. The
reaction was carried out with primary amines instead of
secondary amines under otherwise identical optimized
conditions (shown in Scheme 3). To our delight, various
arylamines bearing para- (3a−i), meta- (3n, 3o), or ortho-
(3j−m) electron-donating, electrom-neutral, or electron-with-
drawing substitutions all afforded the desired isothiocyanates
(4a−o) in good to excellent yields. Tertiary amine, ether,
chloro, bromo, fluoro, trifluoromethyl, and cyano groups are all
tolerated. Ortho hindrance has very little influence on the
transformation. For instance, 2,4,6-trimethylaniline (3k) and
a
Conditions 1: 1.0 mmol of 3, 5.0 mmol of CF3SiMe3, 4.0 mmol of
elemental sulfur, and 3.0 mmol of KF in 20 mL of THF at room
b
c
temperature reacted for 1 h under N2. 12 h. 10 mmol scale.
d
Conditions 2: 0.2 mmol of 3, 0.3 mmol of AgSCF3, and 0.3 mmol of
e
KBr in 4 mL of CH3CN at room temperature reacted for 1 h. 1.0
mmol. Isolated yield (the yields in parentheses with blue color and
the yields of 4x and 4y were obtained under conditions 2; other yields
were obtained under conditions 1).
f
2,6-diisopropylaniline (3l) afforded the corresponding iso-
thiocyanate products 4k and 4l in 94% and 96% yields,
respectively. On a gram scale, product 4k (1.61 g, 9.1 mmol)
was obtained in 91% yield. The pyridine heterocycle was
tolerated (4p). Then various alkyl amines were investigated,
affording the corresponding isothiocyanate products 4q−w in
moderate to good yields. In particular, the alkynyl functionality
was also tolerated (4s). It has been reported that terminal
alkynes react with S8, CF3SiMe3, and KF in DMF under air to
give alkynyl trifluoromethylsulfide products.18a Here, the
chemoselectivity of 3s was changed, leading to the desired
isothiocyanate product 4s with the alkyne preserved.
Compound 4v is unstable on silica gel column chromatog-
raphy, leading to a decreased isolated yield. However, the
stable 4w was obtained in 89% yield. This result is higher than
the yield of 78% from the reported method of Ph3P+CF2CO2−
(PDFA), elemental sulfur, and amantadine at 80 °C.
C
DOI: 10.1021/acs.orglett.9b00383
Org. Lett. XXXX, XXX, XXX−XXX

Organic Letters
Letter
Compounds 3k or 3w react with AgSCF3 under KBr in
CH3CN at room temperature, affording 4k or 4w in almost
quantitative yield (Scheme 3). Sulfamethoxazole (3x) and
sulfamethoxapyridazine (3y) under AgSCF3 and KBr in
CH3CN were also smoothly and selectively transformed to
the corresponding isothiocyanate derivatives 4x and 4y in
quantitative yields, leaving the heterocycles oxazole in 4x and
pyridazine in 4y untouched (Scheme 3).
in CH3CN were also developed, affording the corresponding
thiocarbamoyl fluorides/isothiocyanates at room temperature
in almost quantitative yields, which are characterized by late-
stage application, excellent efficiency, mild reaction conditions,
as well as readily available starting materials. These novel
reactions will promote thiocarbamoyl fluoride bearing N, S, F
elements in a wide variety of applications. Studies on
developing novel methodologies employing thiocarbamoyl
fluorides as useful starting materials are underway in our
laboratory.
20
To know if difluorocarbene was produced from TMSCF3
under our conditions, the reactions of prop-1-en-2-ylbenzene
with TMSCF3 or with TMSCF3 and KF in THF at rt were
performed, but no reaction occurred (SI). ESI-HRMS analysis
of the solution of CF3SiMe3, elemental sulfur, and KF in THF
was performed, and a peak corresponding to SCF3 anion was
observed in the mass spectrum (see the SI). On the bases of
this fact and the experimental observations, although we
cannot totally ruling out difluorocarbene mechanism, more
plausible mechanisms for these novel reactions were proposed
in Scheme 4. CF3SiMe3 in the presence of elemental sulfur and
ASSOCIATED CONTENT
* Supporting Information
■
S
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.or-
glett.9b00383.
Experimental procedures and spectroscopic character-
1
ization data; H and 13C NMR spectra of the new
compounds (PDF)
Scheme 4. Proposed Mechanisms
AUTHOR INFORMATION
■
Corresponding Author
*E-mail: lqjiang@sat.ecnu.edu.cn.
ORCID
Liqin Jiang: 0000-0002-9751-7510
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
We are grateful for financial support from the Science and
Technology Commission of Shanghai Municipality (No.
15ZR1410500) and the sponsorship from the National Natural
Science Foundation of China (No. 21402052).
KF in THF is converted to the SCF3 anion (might be KSCF3)
(Scheme 4, 1). It is well-known that there is an equilibrium
between SCF3 anion with thiocarbonyl fluoride (SCF2) and
fluoride anion (Scheme 4, 2),19b,21 or KSCF3 is unstable and
decomposes to thiocarbonyl fluoride and KF (Scheme 4,
2).18a,21a The secondary amine then reacts with thiocarbonyl
fluoride in THF to afford the corresponding thiocarbamoyl
fluorides (Scheme 4, 3). Primary amines react with the in situ
generated thiocarbonyl fluoride in THF to produce the
corresponding isothiocyanates (Scheme 4, 4). Alternatively,
AgSCF3 reacts with KBr in acetonitrile at room temperature to
afford KSCF3 and AgBr precipitate (Scheme 4, 5). The
formation of KSCF3 then follows the sequences in Scheme 4,
2−4, in acetonitrile to afford the thiocarbamoyl fluorides/
isothiocyanates.
In conclusion, reactions of thiocarbonyl fluoride derived
from CF3SiMe3, elemental sulfur, and KF with secondary
amines or primary amines were developed, affording a variety
of thiocarbamoyl fluorides or isothiocyanates in moderate to
good yields. The two reactions highlight the use of readily
available, cheap, and widely used starting materials, mild
reaction conditions (rt), very broad substrate scope, good
functional tolerance, and gram-scale synthesis with almost
constant yields. The two reactions also represent the first
examples of useful transformations involving thiocarbonyl
fluoride derived from CF3SiMe3, elemental sulfur, and KF.
Reactions of secondary/primary amines with AgSCF3 and KBr
REFERENCES
■
(1) (a) Mingat, G.; MacLellan, P.; Laars, M.; Clayden, J. Org. Lett.
2014, 16, 1252. (b) Baroudi, A.; Alicea, J.; Flack, P.; Kirincich, J.;
Alabugin, I. V. J. Org. Chem. 2011, 76, 1521. (c) Zhou, L.; Tan, C. K.;
Jiang, X.; Chen, F.; Yeung, Y.-Y. J. Am. Chem. Soc. 2010, 132, 15474.
(2) (a) Boebel, T. A. et al. US2011/34492 A1, 2011. (b) Vidaluc, J.-
L.; Calmel, F.; Bigg, D.; Carilla, E.; Stenger, A.; Chopin, P.; Briley, M.
J. Med. Chem. 1994, 37, 689. (c) Alabugin, I.; Baroudi, A. U.S. Pat.
Appl. Publ. 20110237798, 29 Sep 2011. (d) Hays, D. S. et al. U.S. Pat.
Appl. Publ. 20060100229, 11 May 2006. (e) Hays, D. S. et al. PCT
Int. Appl. 2005079195, 01 Sep 2005. (f) Lindstrom, K. J. et al. PCT
Int. Appl. 2005020999, 10 Mar 2005. (g) Lee, B. Y. et al. PCT Int.
Appl. 2001009128, 08 Feb 2001.
(3) (a) Vidaluc, J.-L.; Calmel, F.; Bigg, D.; Carilla, E.; Stenger, A.;
Chopin, P.; Briley, M. J. Med. Chem. 1994, 37, 689. (b) Skorini, S. J.;
Senning, A. Tetrahedron 1980, 36, 539. (c) Neugebauer, F. A.;
Fischer, H.; Krieger, C. J. Chem. Soc., Perkin Trans. 2 (1972-1999)
1993, 3, 535. (d) Rivier, H.; Langer, M. Helv. Chim. Acta 1943, 26,
1722. (e) Chen, W.; Li, R.; Han, B.; Li, B.-J.; Chen, Y.-C.; Wu, Y.;
Ding, L.-S.; Yang, D. Eur. J. Org. Chem. 2006, 2006, 1177. (f) Martvon,
A.; Uher, M. Zbornik Prac Chemickotechnologickej Fakulty SVST 1978,
43.
(4) (a) Walter, W.; Becker, R. F. Justus Liebigs Annalen der Chemie
1972, 755, 145. (b) Brehme, R.; Senkbeil, E. Pharmazie 1979, 34,
372.
(5) (a) Vitaku, E.; Smith, D. T.; Njardarson, J. T. J. Med. Chem.
2014, 57, 10257. (b) Ilardi, E. A.; Vitaku, E.; Njardarson, J. T. J. Med.
Chem. 2014, 57, 2832.
D
DOI: 10.1021/acs.orglett.9b00383
Org. Lett. XXXX, XXX, XXX−XXX

Organic Letters
Letter
(6) (a) Harris, J. F. J. Org. Chem. 1967, 32, 2063. (b) Yarovenko, N.
N.; Vasil’eva, A. S. Zh. Obshch. Khim. 1959, 29, 3754.
(21) (a) Tavener, S. J.; Adams, D. J.; Clark, J. H. J. Fluorine Chem.
1999, 95, 171. (b) Liu, J.-B.; Xu, X.-H.; Chen, Z.-H.; Qing, F.-L.
Angew. Chem., Int. Ed. 2015, 54, 897.
(7) (a) Mukerjee, A. K.; Ashare, R. Chem. Rev. 1991, 91, 1.
(b) Dobosz, M.; Wujec, M. Heterocycles 2002, 57, 1135. (c) Vincent-
Rocan, J.-F.; Beauchemin, A. M. Synthesis 2016, 48, 3625. (d) Posner,
G. H.; Cho, C. G.; Green, J. V.; Zhang, Y.; Talalay, P. J. Med. Chem.
1994, 37, 170. (e) Zhang, X.; Neamati, N.; Lee, Y. K.; Orr, A.; Brown,
R. D.; Whitaker, N.; Pommier, Y.; Burke, T. R., Jr Bioorg. Med. Chem.
2001, 9, 1649. (f) Burke, T. R., Jr; Bajwa, B. S.; Jacobson, A. E.; Rice,
K. C.; Streaty, R. A.; Klee, W. A. J. Med. Chem. 1984, 27, 1570.
(g) Glushko, V. N.; Blokhina, L. I.; Sadovskaya, N. Y. Russ. J. Gen.
Chem. 2015, 85, 2458.
(8) (a) Dufour, V.; Stahl, M.; Baysse, C. Microbiology 2015, 161,
229. (b) Fimognari, C.; Lenzi, M.; Hrelia, P. Curr. Med. Chem. 2008,
15, 440. (c) Traka, M.; Mithen, R. Phytochem. Rev. 2009, 8, 269.
(d) Ioannides, C.; Konsue, N. Drug Metab. Rev. 2015, 47, 356.
(e) Uto, T.; Hou, D.-X.; Morinaga, O.; Shoyama, Y. Adv. Pharmacol.
Sci. 2012, 2012, 614046. (f) Rice, K. C.; Jacobson, A. E.; Burke, T. R.,
Jr; Bajwa, B. S.; Streaty, R. A.; Klee, W. A. Science 1983, 220, 314.
(9) (a) O’Donnell, C. J.; Cloninger, M. J. Thiophosgene. In e-EROS;
John Wiley & Sons, Ltd, 2001. (b) Grayson, J. I. Org. Process Res. Dev.
1997, 1, 240. (c) Dyer, E.; Johnson, T. B. J. Am. Chem. Soc. 1932, 54,
777.
(10) (a) Sun, N.; Li, B.; Shao, J.; Mo, W.; Hu, B.; Shen, Z.; Hu, X.
Beilstein J. Org. Chem. 2012, 8, 61. (b) Munch, H.; Hansen, J. S.;
Pittelkow, M.; Christensen, J. B.; Boas, U. Tetrahedron Lett. 2008, 49,
3117. (c) Xu, X.; Qian, X.; Li, Z.; Song, G.; Chen, W. J. Fluorine
Chem. 2004, 125, 1159.
(11) (a) Barton, D. H. R.; Fontana, G.; Yang, Y. Tetrahedron 1996,
52, 2705. (b) Knox, G. R.; Pauson, P. L.; Willison, D.; Solcaniova, E.;
Toma, S. Organometallics 1990, 9, 301.
(12) Sato, M.; Stammer, C. H. J. Med. Chem. 1976, 19, 336.
(13) Kim, S.; Yi, K. Y. Tetrahedron Lett. 1985, 26, 1661.
(14) (a) Scattolin, T.; Deckers, K.; Schoenebeck, F. Angew. Chem.,
Int. Ed. 2017, 56, 221. (b) Scattolin, T.; Klein, A.; Schoenebeck, F.
Org. Lett. 2017, 19, 1831. (c) Yu, J.; Lin, J.-H.; Xiao, J.-C. Angew.
Chem., Int. Ed. 2017, 56, 16669. (d) Liao, Y.-Y.; Deng, J.-C.; Ke, Y.-P.;
Zhong, X.-L.; Xu, L.; Tang, R.-Y.; Zheng, W. Chem. Commun. 2017,
53, 6073.
(15) Tyrra, W. E.; Naumann, D.; Hoge, B.; Yagupolskii, Y. L. J.
Fluorine Chem. 2003, 119, 101.
(16) (a) Orsi, D. L.; Easley, B. J.; Lick, A. M.; Altman, R. A. Org.
Lett. 2017, 19, 1570. (b) Zheng, J.; Cai, J.; Lin, J.-H.; Guo, Y.; Xiao, J.-
C. Chem. Commun. 2013, 49, 7513. (c) Xiao, J.; Zheng, J.; Cai, J.
CN103965242 B, 2017.
(17) (a) Liu, X.; Xu, C.; Wang, M.; Liu, Q. Chem. Rev. 2015, 115,
683. (b) Chu, L.; Qing, F.-L. Acc. Chem. Res. 2014, 47, 1513. (c) Tom
ashenko, O. A.; Grushin, V. V. Chem. Rev. 2011, 111, 4475. (d) Ma,
J.-A.; Cahard, D. Chem. Rev. 2008, 108, PR1. (e) Ruppert, I.; Schlich,
K.; Volbach, W. Tetrahedron Lett. 1984, 25, 2195. (f) Prakash, G. K.
S.; Krishnamurti, R.; Olah, G. A. J. Am. Chem. Soc. 1989, 111, 393.
(18) (a) Chen, C.; Chu, L.; Qing, F.-L. J. Am. Chem. Soc. 2012, 134,
12454. (b) Chen, C.; Xie, Y.; Chu, L.; Wang, R.-W.; Zhang, X.; Qing,
F.-L. Angew. Chem., Int. Ed. 2012, 51, 2492. (c) Weng, Z.; He, W.;
Chen, C.; Lee, R.; Tan, D.; Lai, Z.; Kong, D.; Yuan, Y.; Huang, K.-W.
Angew. Chem., Int. Ed. 2013, 52, 1548.
(19) (a) Glenadel, Q.; Tlili, A.; Billard, T. Eur. J. Org. Chem. 2016,
2016, 1955. (b) Zhang, M.; Chen, S.; Weng, Z. Org. Lett. 2018, 20,
481. (c) Zheng, J.; Cheng, R.; Lin, J.-H.; Yu, D.-H.; Ma, L.; Jia, L.;
Zhang, L.; Wang, L.; Xiao, J.-C.; Liang, S. H. Angew. Chem., Int. Ed.
2017, 56, 3196. (d) Luo, J.-J.; Zhang, M.; Lin, J.-H.; Xiao, J.-C. J. Org.
Chem. 2017, 82, 11206. (e) Zhen, L.; Yuan, K.; Li, X.; Zhang, C.;
Yang, J.; Fan, H.; Jiang, L. Org. Lett. 2018, 20, 3109. (f) Li, Z.; Dong,
J.; Yuan, Z.; Yang, D.-Y.; Weng, Z. Org. Lett. 2018, 20, 6407.
(20) (1) Wang, F.; Luo, T.; Hu, J.; Wang, Y.; Krishnan, H. S.; Jog, P.
V.; Ganesh, S. K.; Prakash, G. K. S.; Olah, G. A. Angew. Chem., Int. Ed.
2011, 50, 7153. (2) Hu, M.; Ni, C.; Li, L.; Han, Y.; Hu, J. J. Am.
Chem. Soc. 2015, 137, 14496. (3) Li, L.; Ni, C.; Xie, Q.; Hu, M.;
Wang, F.; Hu, J. Angew. Chem., Int. Ed. 2017, 56, 9971.
E
DOI: 10.1021/acs.orglett.9b00383
Org. Lett. XXXX, XXX, XXX−XXX