Regiochemistry of Diels-Alder reaction of hexafluorothioacetone and dienes

Article abstract of DOI:10.1016/j.jfluchem.2016.06.007

The reaction of 2,2,4,4-tetrakis(trifluoromethyl)-dithiethane-1,3 (1) with various hydrocarbon dienes is not regioselective and results in the formation of two isomeric Diels-Alder cycloadducts with the ortho isomer predominating. The reaction of non-conjugated dienes involves ene-insertion of hexafluorothioacetone (HFTA), followed by Diels-Alder reaction of the product of the ene- reaction with a second mole of HFTA, while the reaction of 1,1,4,4-tetramethylbutadiene-1,3 and 2,5-dimethylhexadiene-1,5 results exclusively in HFTA insertion into the allylic C[sbnd]H bond.

Full text of DOI:10.1016/j.jfluchem.2016.06.007

Accepted Manuscript
Title: Regiochemistry of Diels-Alder Reaction of
Hexafluorothioacetone and Dienes
Author: Viacheslav A. Petrov Alexander A. Marchione
Rebecca Dooley Will Marshall
PII:
S0022-1139(16)30152-X
DOI:
Reference:
http://dx.doi.org/doi:10.1016/j.jfluchem.2016.06.007
FLUOR 8792
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Received date:
Revised date:
Accepted date:
28-4-2016
9-6-2016
10-6-2016
Please cite this article as: Viacheslav A.Petrov, Alexander A.Marchione,
Rebecca Dooley, Will Marshall, Regiochemistry of Diels-Alder Reaction
of Hexafluorothioacetone and Dienes, Journal of Fluorine Chemistry
http://dx.doi.org/10.1016/j.jfluchem.2016.06.007
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Regiochemistry of Diels-Alder Reaction of Hexafluorothioacetone and Dienes.
Viacheslav A. Petrov, a*, Alexander A. Marchione, a Rebecca Dooley a and Will Marshall b
Chemours Fluorochemicals a
DuPont Corporate Center for Analytical Sciences b
200 Powder Mill Rd, Experimental Station. E262/339, Wilmington DE 19803
Email: viacheslav.petrov@chemours.com
Keywords: Hexafluorothioacetone; 2,2-4,4-tetrakis(trifluoromethyl)dithietane-1,3; reaction with
dienes.
1

Graphical abstract
F3C CF3
R
R
R
CF3
CF3
25-65oC
S
S
S
+
CF3
+
S
Solvent
CF3
F3C CF3
major isomer
R=CH3, OCH3, OSi(CH3)3, OC(O)CH3
2

Highlights:
 Regiochemistry of Diels-Alder reaction
 Formation of two regio-isomers
 Structural assignment of isomers
Abstract
The reaction of 2,2,4,4-tetrakis(trifluoromethyl)-dithiethane-1,3 (1) with various
hydrocarbon dienes is not regioselective and results in the formation of two isomeric Diels-Alder
cycloadducts with the ortho isomer predominating. The reaction of non-conjugated dienes
involves ene-insertion of hexafluorothioacetone (HFTA), followed by Diels-Alder reaction of the
product of the ene- reaction with a second mole of HFTA, while the reaction of 1,1,4,4-
tetramethylbutadiene-1,3 and 2,5-dimethylhexadiene-1,5 results exclusively in HFTA insertion
into the allylic C-H bond.
Keywords: 2,2,4,4-tetrakis(trifluoromethyl)-ditiethane-1-3; dienes; Diels-Alder reaction; ene-
reaction; regioselectivity.
1. Introduction
Despite the fact that cycloaddition reactions of hexafluorothioacetone (HFTA) and its cyclic
dimer (2,2,4,4-tetrakis(trifluoromethyl)-ditiethane-1-3, 1) with conjugated dienes have been
extensively studied in last 50 years, [1-4] the regioselectivity of the reaction of HFTA and
unsymmetrical dienes is still not perfectly understood. While hexafluoroacetone (HFA) was
reported to react with 2-methylbutadiene-1,3 in regiospecific fashion, producing only 5-methyl-
3

2,2-bis(trifluoromethyl)-3,6-dihydro-2H-pyran in high yield [5], the reaction of HFTA with 2-
chloro-butadiene-1,3 and 1-methoxy-1,3-butadiene reportedly gives a mixture of regioisomers
[6], but unfortunately the publication provides neither experimental details nor spectroscopic
data for the cycloaddition products. The formation of two regioisomers in the Diels-Alder
reaction of HFTA and unsymmetrical dienes seems to be consistent with known data on the
reactivity of HFTA, since C=S in this compound is known to react through nucleophilic attack
either on carbon or sulfur, depending on the character of the nucleophile [7].
Fluorinated thioaldehydes RfCH=S (Rf=H(CF2)2-, H(CF2)4-) 3 were reported to react
with 2-ethoxybutadiene-1 with the formation of two regioisomers [8], while the reaction of
fluorinated aldehydes of similar structure with 2-ethoxybutadiene-1,3 led to highly selective
formation of a single regioisomer [9].
These reports strongly suggest that in contrast to hexafluoroacetone, the monomeric
(CF3)2C=S reacts with unsymmetrical conjugated dienes, with the formation of a mixture of
regioisomers. This hypothesis is consistent with data on the reactivity of hydrocarbon
thiocarbonyls (these reactions usually lead to the mixture of two regioisomers [10] in Diels-
Alder reactions) and also with data on the reactivity of fluorinated thioaldehydes towards 2-
ethoxybutadiene-1,3 [8]. However, literature reports on this subject are contradictory. For
example, the reaction of HFTA with styrenes (as originally discovered by W. Middleton [6] and
lately studied in detail, the reaction of HFTA (or dimer 1 [2, 11, 12]), first step of this process
(which involves a Diels-Alder reaction) proceeds in regiospecific fashion, typically resulting in
selective formation of one regioisomer.
4

This study presents new data clarifying the regiochemistry of the Diels-Alder reaction of
unsymmetrical dienes and HFTA, using readily available cyclic dimer 1 as a source of HFTA
for cycloaddition reactions.
2. Results and Discussion.
Similar to the reaction of 1 and 2,3-dimethylbutadiene-1,3 [3], the CsF-catalyzed reaction of
1 with 1-substituted butadienes-1,3 (2, R=CH3, 4, R=OCH3) proceeded under mild conditions
and resulted in the formation of two regioisomers in each case. (Eq.1)
F3C CF3
R
R
R
CF3
CF3
5-25oC, 16h
CsF, DMF
S
S
S
+
CF3
+
S
CF3
F3C CF3
1
2
4
R=CH3
R=OCH3
3a
5a
3b, yield 69%
5b, yield 59%
ratio 3a:3b - 63:37
ratio 5a:5b - 81:19
.
Eq.1
The reaction of diene 6 ( R=OSi(CH3)3) in the presence of CsF led to the formation of complex
mixture of products, but in the absence of the catalyst, in DMSO solvent [12] , it led to a
mixture of cycloadducts 7a, b isolated in high yield (Eq.2).
R
R
R
CF3
CF3
65oC, 8-12h
DMSO
S
+
CF3
+
1
S
CF3
6
8
R=OSi(CH3)3 7a
R=OC(O)CH3 9a
7b, yield 91%
9b, yield 73%
ratio 7a:7b - 66:34
ratio 9a:9b - 80:20
5

Eq.2
The reaction of diene 8 (R=OC(O)CH3) with 1 was rather slow at ambient temperature (<10%
conversion after 16 h), but at 65oC it was completed after ~ 16 h, producing a mixture of
isomers 9a,b.
It should be pointed out, that regardless of the presence or absence of the catalyst, all
these reactions resulted in the formation of a mixture of isomeric products, with predominance of
more sterically hindered “ortho-like” isomer –(isomers 3a, 5a, 7a or 9a, respectively), even in
the case of diene 6 carrying the bulky –OSi(CH3)3, Typical isomeric ratios were 60:40,
reaching 80:20 in case of dienes 4 ( R=OCH3) and 8 (R=OC(O)CH3). The predominant
formation of “ortho-like” isomers in the crude reaction mixture was observed in all of Diels-
Alder reactions investigated in this work, with only one exception (diene 18, Eq. 8,).
The structural assignment of regio- isomers formed in Diels-Alder involving dienes 2, 4,
6, 8 (and also 10, 18) was based on assignment of structure of isomers 3a and 3b using NMR
spectroscopy. The structures 3a and 3b were assigned to major and minor isomer based on a 13C
INADEQUATE spectrum, which established full carbon connectivity in the structures and
permitted unambiguous structural determination. It should be pointed out that the chemical
shifts of the CF3 resonances in the 19F NMR spectrum of major isomer 3a evinced increased
shielding due to steric interactions with the adjacent carbon. Since same trend was observed in
19F NMR spectra for mixtures of compounds 5a,b, 7a,b and 9a,b (Table 2), the structure of
“ortho-like“ isomer was assigned to major isomers (compounds 5a, 7a and 9a). Because of the
pronounced ability of HFTA to undergo ene- type reaction with olefins having allylic hydrogens
[1, 3, 6, 12-14] it was also possible to involve unconjugated dienes into reaction with 1. For
6

example, pentadiene-1,4 (10) underwent reaction with 1, producing a mixture of two isomeric
cycloadducts 11a,b (ratio 80:20), derived from two sequential processes: – ene- insertion of
HFTA leading to 11c, followed by Diels-Alder reaction with a second mole of HFTA (Eq. 3)
CH2SCH(CF3)2
25oC, 48h
+
1
CsF, DMF
11c
10
S=C(CF3)2
CH2SCH(CF3)2
CH2SCH(CF3)2
CF3
S
+
CF3
CF3
S
CF3
11a
11b
yield 56%, ratio 11a : 11b - 80 : 20
Eq.3
An interesting feature of this reaction was the predominant formation of “ortho-like” isomer 11a,
(ratio 11a:11b= 80:20), despite of the presence of the bulky –CH2SCH(CF3)2 substituent in the
α-position to the carbon bearing two CF3 groups.
The reaction of hexadiene-1,5 (12) with excess of 1 led to the formation of the 1: 3 adduct, with
high predominance of one isomer. (Eq. 4). Compound 13, comprising ~10 % of isomeric
product, was isolated in 55 % yield, but the structural assignment of isomers was not carried out
was in this case.
CH2SCH(CF3)2
25oC, 24h
S
+
1 (exc.)
CF3
CsF, DMSO
CF3
CH2SCH(CF3)2
12
13, 92%
7

Eq.4
The CsF-catalyzed reaction of conjugated diene 14 (ratio trans-, trans- / trans-,cis- isomers –
77:23) with 1 was exothermic (the temperature of the reaction mixture was controlled using a
cooling bath) and led to the formation of two isomers 15a and 15b (Eq. 5)
15-25oC, 24h
S
S
+
CF3
1
CF3
CsF, DMSO
CF3
CF3
14
15a
15b
trans-, trans :
trans-, cis -
77:23
conv. of 14 - 96%,
yield 15a,b - 86%
ratio 15a:15b - 68:32
Eq. 5
By monitoring the reaction progress by NMR, it was confirmed that trans-, trans- isomer
reacted faster than the trans-, cis- isomer; the ratio of 15a : 15b was progressively changing
over time from 91:9 (1 h), to 78: 22 (6h) and finally to 68:32 (24h, at 96% conversion of 14).
The reaction of diene 16 (trans-, trans- isomer) with 1 (carried out in the absence of CsF
catalyst) led to high yield formation of two isomeric products (Eq. 6)
OC(O)CH3
OC(O)CH3
OC(O)CH3
CF3
CF3
S
65oC, 10h
DMSO
S
+
+
1
CF3
CF3
17a,b
16
trans-, trans-
>96%
yield 17a,b - 80%
ratio isomers - 57:43
Eq.6
8

Based on the geometry of starting material 16 (trans-, trans- isomer, 96%) a cis- relationship of
CH3- and –CH2OC(O)CH3 was assumed for both regio- isomers 17a and 17b, since Diels-Alder
reactions proceed through disrotatory cyclization process, leading to the cis- relationship of
substituents in case of trans- trans- dienes [15], however the assignment of isomers was not
carried out in this case.
The geometry of the diene component has a great effect on the regioselectivity of the
Diels-Alder reaction with 1. For example, the addition of 1 to a mixture of dienes 18 (a mixture
of cis- and trans- isomers, ratio 77:23) and CsF catalyst in DMSO, resulted in exothermic
reaction; all cis- isomer was reacted away within 6 h at ambient temperature (NMR). In this case,
the reaction led to the formation of two regioisomers 19a and 19b, but this time with significant
predominance of the “meta-like” isomer 19b (Eq.7). It should be pointed out that “reversed”
regioselectivity observed in this reaction is not well understood at this point.
CF3
15-25oC, 24h
CF3
S
+
+
1
CF3
S
CsF, DMSO
CF3
18
19a
19b
cis/trans
- 77:23
yield 19a,b - 47%
ratio 19a:19b - 27:73
Eq. 7
Extension of the reaction time eventually resulted in full conversion of trans- isomer of 18.
However, it also led to formation of noticeable amounts of 1:2 adduct (up to 14%, mixture of
9

two isomers, ratio 95:5). Although these adducts were not characterized, experimental data
suggest that they evolved from the reaction of trans- isomer with 1, since only trace of these
materials were observed in the reaction mixture in first 6 hours of reaction at 100% consumption
of cis- isomer, but this amount of this fraction went up to 14% after 24 h at ambient temperature.
Dienes carrying several methyl substituents are known to be unreactive in Diels-Alder reaction
due to steric destabilization of cisoid conformation, required for the cycloaddition process. For
example, 1,1,4,4-(tetramethyl)butadiene -1,3 (20) in reaction with bezyne was reported to give
exclusively ene- product. [16] A similar effect was noted in the reaction of 1,1,4,4-
tetaramethylbutadiene-1,3 (20) with 1, in which the diene 21 was formed selectively and was
isolated in 41% yield, along with a small amount of double-insertion product 21a (Eq.8).
25oC, 24h
+
1
CsF, DMF
SCH(CF3)2
20
21, 41%
+
SCH(CF3)2
(F3C)2HCS
21a, 3%
Eq.8
Compound 21a was isolated in low yield from the residue of distillation pot by recrystallization
from hexane, and its structure was established by single crystal X-ray diffraction (Fig.1).
10

Fig. 1. Crystal structure of 21a with thermal ellipsoids draw to the 30% probability level.
Extension of the reaction time up to 10 days (molar ratio 1 : 20 – 2:1, DMSO, CsF catalyst, 25
°C) led to an increase in the yield of 21a (up to 17 %, Eq.9). According NMR, compound 21a
forms as a mixture of isomers (diastereomers) and the fact that only anti-isomer isolated,
probably was related to its limited solubility in the hexane, which was used as a solvent for
recrystallization.
25oC, 10 days
+ 1
CsF, DMSO
SCH(CF3)2
(F3C)2HCS
21
21a, 17%
11

Eq.9
The significantly longer reaction time (10 days vs. 24h) required to increase the yield of 21a,
attests to the difference in rates of insertion of the first and second molecule of HFTA. Since an
ene- reactions proceed through a formation of highly ordered six-membered transition state [17],
followed by migration of a double bond, the introduction of a bulky –SCH(CF3)2 into the α-
position to the reaction center may significantly retard the rate of the second insertion of HFTA
into 21.
The reactivity of diene 22 towards 1 is consistent with this model, since the diene gave
the product of double insertion of HFTA (diene 23) after only 24 h (Eq.10). Compound 23
formed as a mixture of isomers, with a high predominance of trans-, trans- isomer, which was
isolated in 38% yield (Eq. 10).
SCH(CF3)2
25oC, 24h
+
1
CsF, DMF
(F3C)2CHS
22
23, 38%
Eq.10
The structure of compound 23 was established by single crystal X-ray diffraction (Fig.2).
12

Fig. 2 Crystal structure of 23 with thermal ellipsoids draw to the 30% probability level.
Regio-Chemistry of Diels-Alder Reactions involving HFTA.
The results obtained in this study indicate that the Diels-Alder in the reaction of HFTA
with dienes 2,4,6,8, and 10 the more sterically hindered “ortho-like” isomers (3a, 5a, 7a, 9a and
11a, Eq. 1-4) are formed preferentially. While the ratio of regioisomers fluctuated depending on
the substituents at the terminal carbons of the diene, formation of the “ortho-like” isomer was
13

invariably favored in these reactions. The root cause of this phenomenon is not well understood
at this point, but computational studies may shed some light on this problem.
Although the structural assignment of isomers was based on the difference in 19F chemical shifts
of CF3 moieties in the various isomers (vide supra), an additional confirmation of the assignment
was obtained in the case of cycloadducts 7a,b. An isolated sample of isomers 7a,b (ratio 1:1,
isolated by distillation), underwent complete decomposition upon storage in a glass ampule
under ambient conditions for 4.5 y. NMR analysis of this material confirmed the absence of
either 7a or 7b, but instead, a mixture of alcohol 24a, compound 24b [6] and [(CH3)3Si]2O
were observed in the mixture, in a ratio ~1:1:1.
OH
25oC,
4.5 years
OSi(CH3)3
OSi(CH3)3
CF3
CF3
CF3
S
S
+
CF3
glass
CF3
S
+
CF3
S
CF3
CF3
24a
24b
7a
7b
+ [(CH3)3SI]2O
Eq.11
A pure sample of alcohol 24a was isolated by crystallization, and its structure was confirmed by
single crystal X-ray diffraction (Fig.3) and compound 24b was isolated as a mixture with
[(CH3)3Si]2O, but was fully characterized by NMR spectroscopy (Table 2).
14

Fig. 3. Crystal structure of 24a with thermal ellipsoids draw to the 30% probability level.
While the formation of compound 24a can be rationalized as being a result of hydrolysis of
isomer 7a by moisture, the formation of 24b can be explained as a result of 1,4-elimination of
“HOSi(CH3)3”, due to the presence of a relatively acidic proton in α-position to electron
withdrawing CF3-groups in isomer 7b (Eq.12)
15

OSi(CH3)3
CF3
OH
CF3
CF3
H2O
CF3
S
S
+ [(CH3)3SI]2O + H2O
7a
24a
OSi(CH3)3
OSi(CH3)3
-H+
S
S
CF3
CF3
CF3
CF3
H
H
H
7b
-(CH3)3SiO-
S
+ [(CH3)3SI]2O + H2O
CF3
CF3
24b
Eq.12
It should be pointed out that 2-H-thyopyranes, structurally similar to 24b, were prepared by
selective reaction of the “meta-like” isomer derived from the reaction of RfCH=S [Rf=H(CF2)2-
and H(CF2)4-] and 1-EtO-butadiene-1,3 in a HCl/i-PrOH mixture [8]. Reported 1H NMR data of
these materials [8] are in good agreement with 1H NMR data of 24b obtained in this work (Table
2).
Both structures of 24a and 24b also agreed well with proposed structures of products derived
from Diels-Alder reaction of 6 and 1. The confirmation of the structure of 24a by single crystal
X-ray diffraction can be considered as another example of the predominate formation of the
“ortho-like” isomer in Diels-Alder reactions of HFTA with conjugated dienes. It should be
pointed out that in this respect HFTA resembles closely S=C[C(O)OMe]2, reported to give
16

predominantly “ortho-like“ isomer in reaction with pentadiene-1,3 (ratio of “ortho-“/“meta-“
isomers was 5:1 [18]), while the regioselectivity in reaction of fluorinated thioaldehydes RfCH=S
with 1-EtO-butadiene-1,3 was opposite – in this case “meta-like“ isomer was formed
preferentially (ratio “ortho-“:“meta-“ isomers was 1:2 [8]). It should be pointed out that this
regioselectivity is unusual, since based on results reported in ref. [10], thioaldehydes RCH=S
carrying electron withdrawing groups reported to give predominantly “ortho-like“ isomers in
reaction with Danishefsky diene. It is not clear at this point whence the differing preferences in
regiochemistry stems between HFTA and fluorinated thioaldehydes RfCH=S. Computational
studies may elucidate this problem, since it was reported [10] that in the case of hydrocarbon
thioaldehydes the regiochemistry of cycloaddition process correlates well with the LUMO
coefficient of the C=S bond.
4. Experimental
1H, 13C{H} and 19F NMR spectra were generally acquired on a Varian VNMRS 500
MHz spectrometer equipped with a 5 mm 13C-31P {1H,19F} probe. The INADEQUATE
spectrum was acquired on a Bruker Avance I 500 MHz spectrometer equipped with a 5 mm
13C{1H} helium cryoprobe. CFCl3 or TMS were used as an internal chemical shift standards
and CDCl3 as a lock solvent. GC and GC/MS analyses were carried out on a HP-6890
instrument, using HP FFAP capillary column and either TCD (GC) and mass selective (GS/MS)
17

detectors, respectively. Anhydrous DMF, THF, ACN and DMSO, dienes
2,4,6,8,10,12,14,16,18,20 and 22 (Aldrich) were purchased and used without further purification;
dienes 2, 4, 6, 8, 14, 16, 18 were analysed by NMR to determine ratio of isomers:
Comp. No
Ratio of isomers trans-,trans- to trans/cis
>96:4 trans-
2
4
>96:4 trans-
65:35 trans-/cis-
6
96:4 trans/cis
8
77:23 (trans-,trans- : trans/cis
96:4 (trans-,trans- : trans/cis)
23:77 (trans/cis)
14
16
18
Compound 1 was prepared according modified procedure [19] using CsF as a catalyst. For all
experiments not purified compound 1 was used (purity ~96-98%, reminder cyclic trisulfide
C6F12S3 and a trace of DMF, GC/MS).
Due to a high ratio of sulfur to fluorine, elemental analysis was not attempted for new
materials. The purity of all isolated compounds (established by GC and NMR spectroscopy) was
at least 98%, unless it is stated otherwise.
4.1.Crystallography:
18

X-ray data for 21a, 23 and 24b were collected at -100 ˚C using a Bruker 1K CCD system
equipped with a sealed tube molybdenum source and a graphite monochromator. The structures
were solved and refined using the Shelxtl [20] software package, refinement by full-matrix least
squares on F2, scattering factors from Int. Tab. Vol. C Tables 4.2.6.8 and 6.1.1.4.
Crystallographic data (excluding structure factors) for the structure in this paper has been
deposited with the Cambridge Crystallographic Data Centre as supplementary publication nos.
CCDC #1445792 - #1445794. Copies of the data can be obtained, free of charge, on application
to CCDC, 12 Union Road, Cambridge CB2 1EZ, UK, (fax: +44 1223 336033 or e-mail:
deposit@ccdc.cam.ac.uk).
4.2. Reaction of Compound 1 with Dienes 2,4,6,8,10,12,14,16,18,20,22 (typical procedure).
A mixture of 12-35 mmol of 1 (~10-20 mol % excess), 20-60 mmol of the corresponding
substrate, in 12-15 mL of dry DMSO or DMF [optionally in the presence of 0.3-0.5 g (2-3
mmol) of dry CsF] was agitated at 25-65oC for period of time specified in Table 1. The
reaction progress was monitored by GC and NMR. The reaction mixture was diluted by water
(20-300 mL) and extracted by hexane (2x 50-70mL). The organic layer was washed with water
(2x100-200 mL), and dried over MgSO4. The solvent was removed under vacuum and the
residue was distilled under reduced pressure. Compounds 21a and 23 were isolated by
crystallization from hexane. Reaction conditions, ratio of reagents, conversions and mass-
spectrometry data are given in Table 1 and NMR data for new materials and are given in Table 2.
19

4.2. Isolation of products 24a and 24b.
A sample (3g) of 1:1 mixture of 7a and 7b, which was stored in glass sample vial for 4.5
years, was analysed by NMR and GC/MS. It was found to be a mixture of 24a, 24b and
hexamethyldisiloxane (HMDS) in ratio ~ 1:1:1. Sample was placed under vacuum (1 mm Hg)
and a mixture of 24b and HMDS (1.9 g, mixture ~1:1) was collected in cold trap (-78oC) and
residue (~0.8 g) crystalized upon standing at ambient temperature. It was recrystallized from
hexane to give 0.6 g of 24a.
Acknowledgement:
Technical support by Tim Bentz is greatly appreciated.
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[16] E.M. Arnett, J. Org. Chem. 25 (1960) 324-327.
[17] S. Sankararaman, Pericyclcic Reactions -A Textbook, pp. 329-349, Wiley-VCH, Weinheim, Germany
2005.
[18] S. Perreault, M. Poirier, P. Leveille, O. Rene, P. Joly, Y. Dory, C., J. Org. Chem. 73 (2008) 7457-7466.
[19] V.A. Petrov, W. Marshall, J. Fluorine Chem. 131 (2010) 1144-1155.
[20] G. Sheldrick, (SHELXTL Sofware Suite, v. 6.0, Bruker Axes Corp., Madison WI, 1996.
21

Table 1. Reaction of compound 1 with dienes – reaction conditions, yields, ratio isomers,
and mass-spectrometry data. a
Cata
Entr Com Tem Tim Scale Solve
Yiel Ratio
B.P.
mm/
MS
lyst
(mm
ol)
y
p. No p.
(oC)
e
(mmo nt c
l) b
d
isomer (o,
(m/z)
No
(h)
(%) d s (in
crude) Hg)
81-
1
2
5-25
5-25
16
16
70
60
DMF CsF
(3)
69
59
250
3a,b
5a,b
3a:3b-
84/30
63:37
(M+,
C8H8F6S+)
117-
DMF CsF
(2)
266
5a:5b-
119/50
81:19
(M+,
C8H8F6OS+)
324
DMSO
61-
3
4
25-
48
12
60
30
---
91
73
7a,b
9a,b
7a:7b-
70/1.5 (M+,
50 e
66:34
C10H14F6OSSi+)
65e
25
25
---
294
DMSO
96-
9a:9b-
100/10
80:20
(M+,
C9H8F6O2S+)
431[(M-H)+,
101-
5
6
48
16
20
20
DMF CsF
(2)
56
92
11a,b
11a:11
b-
103/1.2
+
C11H7F12S2 ]
80:20
13
628 (M+,
99.5-
DMF CsF
13
22

+
105/0.
2
(2)
C15H10F18S3 )
DMSO
DMSO
DMSO
99.5-
105/0.
2
7
8
9
25
65
16
8
60
60
60
CsF 86 f
(3)
264(M+,
15a,b
17a,b
19a,b
15a:15
b-
C9H10F6S+)
68:32
17a:17
b-
78-
---
80
47
322
(M+,C11H12F6
O2S+)
80/1.1
57:43
19a:19
b-
264(M+,
C9H10F6S+)
28-
15-
25
24
CsF
(3)
29/0.2
27:73
---
105-
10
11
25
25
24
50
25
DMF CsF
(3)
34
17
292 (M+,
21
109/50 g
C11H14F6S+)
474(M+,
DMSO
10 d
CsF
---
(108-
21a
+
(2)
109)i C14H14F12S2 )
Mixture
of
12
13
25
25
24
50
30
DMF CsF
(3)
38
(103- 474(M+,
23
104)i C14H14F12S2 )
+
isomers
24a: 252(M+,
Quant.
24a:24b:
HMDSj
-
4.5
year
s
---
---
---
24a,b
C7H6F6OS+)
1:1:1
24b: 234(M+,
23

C7H4F6S+)
a see Sec. 4.2 for general procedure
b based on diene; 10-20 mol % excess of 1 was used in all experiments
c 50 mL
d isolated yields; conversion of diene at least 99%, unless stated otherwise
e delayed exotherm (up to 50oC in 5 h)
f at 96%conversion of 14
g distilled material crystallized in freezer at -20oC; liquid at ambient temperature.
i melting point
j
HMDS - hexamethyldisiloxane
24

1
Table 2. H and 19F NMR data for new materials.a
Entry Comp. 1H NMR (δ, ppm, J, Hz)
19F NMR (δ, ppm, J, Hz)
No
No
3ab
1
1.36(3H, dm, 7.2), 2.86(1H,m),
3.21(1H, dd, 16.5, 5.0), 3.28(1H, d,
16.5), 5.68(1H, dm, 10.3), 5.96(1H,
dm, 10.3)
-63.69(3F, q, 11.0), -67.53(3F, q,
11.0)
3bc
2
1.39(3H, dm, 7.1), 2.43(1H,dm,17.1), -70.65(m)
), 2.81(1H, dd, 17.1, 5.3), 3.64(1H,
m), 5.87(1H, dm, 10.3), 6.00(1H, dm,
10.3)
3
4
5
3.17(1H, d, 17.0), 3.35(1H,dd, 17.0,
-63.22(3F, q, 9.5), -67.82(3F, q, 9.5)
5a
5b
7a
7b
4.8), 3.50(3H,s), 4.26(1H,s),
5.95(1H,d, 10.5), 6.15(1H,d, 10.5)
2.70(1H, dd, 16.6,5.4). ), 2.81 (1H,d, -70.27(3F, q, 10.5), -71.10(3F, q,
16.5), 3.45(3H,s), 5.04(1H,d, 5.4),
6.04(1H, m), 6.26(1H, m)
10.5)
0.00(9H,s), 2.98(1H, d, 16.0),
3.16(1H,dd, 16.0, 5.0), 4.61(1H,s),
5.58(1H,d, 10.3), 5.89(1H,d, 10.3)
0.04(9H,s), 2.32(1H, dm, 17.0),
2.71(1H,dd, 17.0, 5.8), 5.34(1H,s),
-62.90(3F, q, 10.0), -67.20(3F, q,
10.0)
-70.11(3F, q, 10.8), -70.92(3F, q,
10.8)
25

5.74(1H, dm, 9.6), 5.98(1H,dm, 9.6)
2.11(3H,s), 3.20(1H, d, 17.3),
3.42(1H,d, 18.2, 4.5), 6.09(2H,m),
6.24(1H,d, 4.8)
6
7
8
9
-63.51(3F, q, 10.0), -68.48(3F, q,
10.0)
9a
9b
2.08(3H,s), 2.76(1H, dm, 18.2),
-69.83(3F, q, 10.8), -70.73(3F, q,
2.84(1H,dd, 17.3), 5.66(1H,dd, 10.7, 10.8)
2.2), 6.01(1H,s), 6.13((1H,m)
2.89(2H,m), 3.16(2H,m),
-63.25(3F, q, 10.0), -66.04(3F, quint,
11a
11b
3.44(1H,m), 3.61(1H. sept., 7.3),
5.95(1H,d, 10.2), 6.22(1H,d, 10.2)
2.60(1H,d, 18.0), 2.81(1H,d,18.0),
3.08(2h,m), 3.44(1H,m), 3.76(1H.
sept., 7.3), 6.00(1H,dm, 11.0),
6.09(1H,dm, 11.0)
9.2), -66.54(3F, quint., 9.2), -
67.02(3F,q, 10.0)
-66.17(3F,m), -66.25(3F, m),
-70.46.02(6F, m)
13d
10
Major isomer:
Major Isomer:
2.80(1H,d, 11.4), 3.00(1H,t, 11.4),
3.11(2H,m), 3.63(1H, sept., 7.3),
3.74(1H, sept., 7.5), 3.82(1H,m),
6.01(1H, dt, 10.2, 3.0), 6.21)1H, dt,
10.2, 2.8)
-63.30(3F,q, 10.0), -66.14(6F, m), -
66.30(3F,m), -66.46(3F, m), -
66.66(3F,q, 10.0
Minor isomer:
-62.82(3F,quint., 8.9), -
63.10(3F,quint., 8.9) -68.83(3F,q,
9.6), -69.78(3F, q, 9.6),
26

11
12
13
1.38(3H,d, 7.0), 1.40(3H,dm, 6.7),
-64.17(3F, q, 10.3), -67.44(3F,q,
15a
15b
17a
2.68(1H,m), 3.61(1H,m), 5.66(1H,dt, 10.3)
9.8, 3.4), 5.88(1H, dt, 9.8, 2.7)
1.32(3H,dm, 7.0), 1.35 (3H,dm, 7.1), -62.73(3F, q, 10.6), -67.57(3F,q,
3.09(1H,m), 3.75(1H,m), 5.54(1H,dt, 10.6)
11.0, 2.7), 5.74(1H, dt, 11.0, 2.4)
1.40(3H,d, 7.0), 2.06(3H,s),
-64.60(3F, q, 10.6), -67.34(3F,q,
10.6)
2.80(1H,dm, 5.6), 3.64(1H,q, 5.7),
4.23(1H,t, 10.4), 4.58(1H, dd, 10.4,
4.1), 5.84(1H, dt, 10.2, 2.3), 6.0(1H,
10.0, 2.9)
14
1.37(3H,dq, 7.0, 2.1), 2.08(3H,s),
2.78(1H, quint, 2.8), 3.88(1H,m),),
4.23(1H,t, 10.4), 4.14(1H, dd, 10.4,
8.1),4.30 (1H,dd, 10.4, 6.7), 5.76(1H,
ddd, 9.7, 4.5, 2.0), 5.84(1H, dm, 9.7)
1.30(3H, dq, 6.7, 2.4), 1.80(3H,m),
2.71(1H,m), 3.21(1H, dq, 15.6, 3.4),
3.27 (1H, dd, 15.6, 3.9), 5.69(1H, tq,
4.9, 1.3)
-63.89(3F, q, 10.7), -67.28(3F,q,
10.7)
17b
15
16
-64.66(3F,qq, 12.2, 2.4), -67.99(3F,
q, 12.2)
19a
19b
1.41(3H, d, 7.3), 1.83(3H, m),
2.47(1H,dd, 16.3, 5.6), 2.71(1H,dd,
16.3, 5.5),3.54(1H, q, 7.5), 5.60(1H,
-70.80(3F,q, 10.0), -70.52(3F, q,
10.0)
27

t, 5.3)
17
18
1.73(3H,s), 1.79(3H,s), 1.82(1H,s),
3.52(1H, sept., 8.4), 4.43(1H, d,9.7),
4.93(1H,s), 5.02(1H, s), 5.19(1H,d,
9.7)
-65.84(3F, quint., 8.4), -66.73(3F,
quint., 8.4)
21
21ae
1.82(3H,s), 1.79(3H,s), 3.61(1H,
sept., 7.8), 3.63(1H,s), 4.93(1H,s),
5.02(1H, s), 5.28(1H,quint., 1.3)
1.88(6H,s), 3.40(4H,m), 3.48(2H,
sept, 7.4), 6.10(2H,s)
-65.39(3F, quint., 8.9), -67.00(3F,
quint., 8.9)
19
20
-66.39(d, 7.4)
23
2.27(1H, br. s, OH), 3.l27(2H,m),
-63.40(3F,q, 10.3), -67.34(3F, q,
24a
4.72(1H, m, 1.2), 5.93(1H, dm, 10.3), 10.3)
6.12(1H, dd, 10.6, 6.5)
5.40(1H,d, 10.6), 6.10(1H, dd, 9.8,
6.4), 6.24(1H,d, 9.8), 6.40(1H,dd,
10.6, 6.4)
-72.94(s)
24b
a in CDCl3 as lock solvent
b 13C {1H} NMR: 17.65, 24.98(sept., 25.4), 31.83,59.29, 123.99, 125.0(m, CF3), 132.66 ppm
b 13C {1H} NMR: 19.70, 24.73(sept., 1.8), 33.65, 58.10(sept., 26.9), 124.02, 125.0(m, CF3),
133.20 ppm
d sample contained 10 mol % of isomeric material
e 13C {H} NMR: 14.73, 50.00(sept., 33.0), 54.41, 121.29, 122.98 (q, 280.0), 125.50(q, 282.0),
138.64 ppm
28