Photoredox-Induced Functionalization of Alkenes for the Synthesis of Substituted Imidazolines and Oxazolidines

Article abstract of DOI:10.1021/acs.joc.6b02377

A one-pot, three-component cascade reaction combining photoredox catalyzed radical addition and formal [3 + 2] annulation was developed. With this approach, highly concise syntheses of imidazoline and oxazolidine derivatives have been achieved. The advantages of this transformation are good to excellent yields, mild reaction conditions, operational simplicity, and easy accessibility of raw materials.

Full text of DOI:10.1021/acs.joc.6b02377

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Article
Photoredox-Induced Functionalization of Alkenes for the
Synthesis of Substituted Imidazolines and Oxazolidines
Jian-Qiang Chen, Wan-Lei Yu, Yun-Long Wei, Teng-Hui Li, and Peng-Fei Xu
J. Org. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.joc.6b02377 • Publication Date (Web): 02 Dec 2016
Downloaded from http://pubs.acs.org on December 2, 2016
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Photoredox-Induced Functionalization of Alkenes for the Synthesis
of Substituted Imidazolines and Oxazolidines
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JianꢀQiang Chen,† WanꢀLei Yu,† YunꢀLong Wei,† TengꢀHui Li,‡ and PengꢀFei Xu*,†
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†State Key Laboratory of Applied Organic Chemistry, Lanzhou University, Lanzhou, 730000, P.R.
China
‡The High School Attached to Northwest Normal University, Lanzhou, 730000, P.R. China
ABSTRACT
A oneꢀpot, threeꢀcomponent cascade reaction combining photoredox catalyzed radical addition and
formal [3+2] annulation was developed. With this approach, highly concise syntheses of imidazoline
and oxazolidine derivatives have been achieved. The advantages of this transformation are good to
excellent yields, mild reaction conditions, operational simplicity and easy accessibility of raw
materials
.
KEYWORDS
photochemistry, cycloaddtion, cascade reaction, imidazolines, oxazolidines
INTRODUCTION
Nitrogenous heterocyclic compounds are widely found in nature.1 Some examples include imidazolines
and oxazolidines, which have been commonly used as biologically active molecules,2 organic synthetic
intermediates,3 and organocatalysts.4 Especially, imidazolines have long been used as auxiliary groups5
and metal complexation ligands6 for asymmetric synthesis. Therefore, as shown in Scheme 1, it is not
surprising that the syntheses of imidazoline and oxazolidine derivatives have been extensively
investigated. In general, 1,2ꢀdiamine and 1,2ꢀamino alcohol, which are not easily available, can be
smoothly transformed into the corresponding imidazoline and oxazolidine under harsh conditions,7
respectively. Besides that, Lewis acid mediated [3+2] cycloaddition of Nꢀtosylaziridines with nitriles or
carbonyls, as an alternative approach, was applied to the syntheses of imidazolines or oxazolidines.8
However, Nꢀtosylaziridines had to be synthesized from 1,2ꢀamino alcohol.9 Recently, Yeung et al.
developed the cationic Br or Cl initiated imidazoline synthesis from olefin by a twoꢀstep
transformation.10 Therefore, the development of novel methods to transform the unactivated alkenes
directly into imidazolines and oxazolidines under mild reaction conditions will be highly desired.
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More recently, owing to its ability to implement the incredible conversion reactions under benign
conditions, visibleꢀlight photocatalysis has attracted a great deal of attention from the chemistry
community.11 Recent studies have shown that the Nꢀcentered radical, generated from the unactivated
substrates by photoredox catalysis, could be employed in the cyclization and crossꢀcoupling reactions.12
We envisioned that the construction of imidazolines or oxazolidines from alkenes might also be
realized through visibleꢀlight photoredox catalysis under mild conditions.
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Scheme 1. The Synthesis of Imidazoline and Oxazolidine Derivatives
RESULTS AND DISCUSSION
To accomplish this goal, we first examined the reaction of styrene and NꢀTsꢀprotected
o
1ꢀaminopyridinium13 at 20 C in the presence of acetonitrile, a 25 W blue LED strip, and 1 mol % of
Ru(bpy)3(PF6)2. The functionalization of alkenes for the synthesis of substituted imidazolines occurred
under these conditions. The choice of photocatalysts was a significant factor to promote this reaction.
When Ir(ppy)3 was used in place of Ru(bpy)3(PF6)2, 3a was obtained in 59% yield (entry 3 in Table 1),
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while no reaction occurred with other organic photocatalysts such as Methylene blue and Eosin Y. To
further improve the yield of the desired product, 2ꢀmethylꢀ4ꢀphenylꢀ1ꢀtosylꢀ4,5ꢀdihydroꢀ1Hꢀimidazole
(3a), the equivalent ratio of Nꢀcentered radical source to styrene was increased, and the yield was
dramatically improved (to 95%, entry 8 in Table 1). Finally, control experiments revealed that both the
photocatalyst and the light source were necessary for the synthesis of imidazoline derivatives.
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Table 1. Screening of the Reaction Conditions for the Synthesis of Imidazolinea
entry
photocatalyst
yield (%)b
1a:2a
1
Ru(bpy)3(PF6)2
Ir(ppy)2(dtbbpy)PF6
Ir(ppy)3
1:1.5
1:1.5
1:1.5
1:1.5
1:1.5
1:2
52
58
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0
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5c
Methylene blue
Eosin Y
0
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Ir(ppy)3
68
78
95
0
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Ir(ppy)3
1:3
8
Ir(ppy)3
1:4
9
ꢀ
1:4
10d
Ir(ppy)3
1:4
0
aUnless otherwise noted, reaction conditions are as follows: 1a (0.2 mmol), 2a (1.5 ꢀ 4 equiv),
o
photocatalyst (0.002 mmol), CH3CN (4 mL), 25 W blue LED strip, 20 C, under N2 atmosphere.
bIsolated yield. c25 W white LED strip was used. dIn the absence of a light source.
Having successfully identified the optimal reaction conditions, we next turned our attention to
examining the scope of the substrates. As shown in Table 2, a variety of substituted alkenes were
readily converted to the corresponding imidazolines using Ir(ppy)3 as the photocatalyst. Interestingly,
when Nꢀbenzenesulfonyl protected 1ꢀaminopyridinium salt was used instead of NꢀTsꢀprotected reactant,
the yield of the product was only slightly diminished (3a vs 3b). Substrates with electronꢀwithdrawing
(3c−3g) and electronꢀdonating (3h−3k) groups in the aromatic ring, including a halogen atom and a
methyl group, could proceed smoothly to give the corresponding substituted imidazolines in good to
excellent yields. Notably, the substrate with a bulky tertꢀbutyl group was also converted into the
corresponding target compound 3k in 84% yield. Furthermore, the transformations of the indene and
1,2ꢀdihydronaphthalene were observed as well in high yields without any undesired diastereomers
(3l−3m). In addition, αꢀmethylstyrenes were also readily transformed into the imidazolines bearing a
tetrasubstituted carbon quaternary stereocenter moiety in high yield (3n−3o). Except for acetonitrile,
other nitriles, such as propiononitrile, cyclopropaneꢀcarbonitrile and benzonitrile, could also achieve
this kind of transformation under the photoredox catalysis conditions (3p−3r). However, the
transformation of some heterocyclic aromatic and nonꢀconjugated alkenes was not success.
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Table 2. Scope of the Substrates for the Synthesis of Imidazoline Derivativesa.b
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aReaction conditions: substrate
R3CN (anhydrous, 4 mL) at 20 C under irradiation by 25 W blue LED strip for 12 h. Isolated
1
(0.2 mmol), substrate
2
(0.8 mmol), Ir(ppy)3 (0.002 mmol) in
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b
yields.
Encouraged by the results described above, we expected that the substituted oxazolidines might
also be generated under similar reaction conditions. The transformation was smoothly realized (entry 1
in Table 3) under the similar reaction conditions when Ir(ppy)3 was used as photocatalyst, and the
examination of the photocatalysts indicated that Ir(ppy)2(dtbbpy)PF6 produced the highest yield and
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took the shortest time to complete the reaction. Interestingly, the optimal equivalent ratio of
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N
ꢀcentered radical source to styrene was 1:1.5 in this case, either increasing or decreasing the
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equivalent ratio would reduce the yield of substituted oxazolidine (entries 3−5 in Table 3).
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Table 3. Screening of the Reaction Conditions for the Synthesis of Oxazolidinea
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entry
photocatalyst
time (h)
1a:2a
yield (%)b
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Ir(ppy)3
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1:1.5
1:1.5
1:1.5
1:2
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Ru(bpy)3(PF6)2
Ir(ppy)2(dtbbpy)PF6 2.5
Ir(ppy)2(dtbbpy)PF6 2.5
Ir(ppy)2(dtbbpy)PF6 2.5
1:1
aUnless otherwise noted, reaction conditions are as follows: substrate 1a (0.2 mmol), 2a (1ꢀ2
o
equiv), photocatalyst (0.002mmol), acetone (anhydrous, 4 mL), 25 W blue LED strip, 20 C,
under N2 atmosphere. bIsolated yield.
With the reaction conditions optimized, we next sought to examine the scope of olefins that can
be applied to this cyclization reaction. As shown in Table 4, this protocol permitted the direct
threeꢀcomponent cyclization of Nꢀcentered radical and acetone with a wide range of unactivated olefins.
Furthermore, both electronꢀwithdrawing and electronꢀdonating substituents in the aromatic ring were
well accommodated in this conversion under the photoredox catalysis. A variety of substituted
oxazolidines were synthesized by this simple method in good to high yields (4a-4i). Likewise,
αꢀmethylstyrenes could also be easily transformed into the oxazolidines bearing an allꢀcarbon
quaternary stereocenter moiety in high yields (4j-4k). In a word, the reaction described herein makes
an important complementation to the transformation which mentioned above.
The configuration of compound 4i was determined by Xꢀray crystal structure analysis. The data of
Xꢀray crystal structures can be found in the Supporting Information.14
Table 4. Scope of the Substrate for the Preparation of Oxazolidine Derivativesa,b
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aReaction conditions: substrate 1 (0.2 mmol), substrate 2a (0.3 mmol), Ir(ppy)2(dtbbpy)PF6 (0.002
o
mmol) in acetone (anhydrous, 4 mL) at 20 C under irradiation by 25 W blue LED strip for 2.5 h.
bIsolated yields.
Control experiments have shown that both the photocatalyst and visible light were involved in the
synthesis of substituted imidazolines. On the basis of our previous work as well as other reports,15
a
plausible reaction mechanism is illustrated in Scheme 2. Irradiation of the photoredox catalyst Ir(ppy)3
with a blue LED strip will generate the photoexcited species *Ir(ppy)3, which is a strong electron donor
to reduce the substrate 2a.16 The NꢀTsꢀprotected 1ꢀaminopyridinium 2a accepts a single electron from
+
*Ir(ppy)3 and then provides the highly activated Nꢀcentered radical (5) and the oxidized Ir(ppy)3 . The
+
species 5 will react with alkene (1) and then afford the stabilized carbon radical (6). Ir(ppy)3 is a
powerful oxidant which will be reduced by species 6 and then converted to the ground state
photocatalyst. The generated carbocationic intermediate (7) is attacked by nitrile to form the highly
reactive intermediate (8). Finally, the cyclization of intermediate 8 leads to the formation of the
imidazoline product. Likewise, the reaction for synthesis of oxazolidine follows the similar mechanism
as we proposed. We also confirmed that this nitrogen radical had multiple reaction sites.
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Scheme 2. Proposed Mechanism
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CONCLUSION
In conclusion, we have developed a direct and concise approach to achieve the visible light
photoredoxꢀinduced functionalization of alkenes for the synthesis of imidazoline and oxazolidine
derivatives. This method achieved a oneꢀpot, threeꢀcomponent cascade reaction through the
combination of photoredox catalyzed radical addition and formal [3+2] annulation. In contrast to
traditional methods, the advantages of this transformation are good to excellent yields, mild reaction
conditions, operational simplicity and easy accessibility of raw materials.
EXPERIMENTAL SECTION
General Information. All glassware was thoroughly ovenꢀdried. Chemicals and solvents were either
purchased from commercial suppliers or purified by standard techniques. Thinꢀlayer chromatography
plates were visualized by exposure to ultraviolet light and/or staining with phosphomolybdic acid
followed by heating on a hot plate. Flash chromatography was carried out using silica gel (200−300
1
mesh). H NMR and 13C NMR spectra were recorded on a 400 MHz spectrometer. The spectra were
1
recorded in deuterochloroform (CDCl3) as solvent at room temperature, H and 13C NMR chemical
shifts are reported in ppm relative to the residual solvent peak. The residual solvent signals were used
as references and the chemical shifts were converted to the TMS scale (CDCl3: δH = 7.26 ppm, δC =
77.0 ppm). Data for 1H NMR are reported as follows: chemical shift (δ ppm), multiplicity (s = singlet,
d = doublet, t = triplet, m = multiplet, dd = doublet, br = broad), integration, coupling constant (Hz) and
assignment. Data for 13C NMR are reported as chemical shift. IR spectra were recorded on a FTꢀIR
instrument and are reported in wave numbers (cmꢀ1). HRMS spectra using ESI were recorded on an
ESIꢀFTMS mass spectrometer.
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General Procedure for the Synthesis of Imidazoline Derivatives. Substrate 1 (0.2 mmol) and
NꢀTsꢀprotected 1ꢀaminopyridinium 2 (0.8 mmol) were added to a solution of photocatalyst Ir(ppy)3 (1
mol%) in nitrile (4 mL) at room temperature. The heterogenous mixture was degassed by three cycles
of freezeꢀpumpꢀthaw and then placed in the irradiation apparatus equipped with a 25 W blue
o
lightꢀemitting diode (LED) strip. The resulting mixture was stirred at 20 C until the starting material
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was completely consumed after 12 h. Upon completion of the reaction, the reaction mixture was
evaporated under reduced pressure, and the resulting crude mixture was purified on silica gel flash
column chromatography using ethyl acetate/hexanes (1/2) eluent to give the corresponding imidazoline
derivatives.
General procedure for the synthesis of oxazolidine derivatives. Substrate 1 (0.2 mmol) and
NꢀTsꢀprotected 1ꢀaminopyridinium 2 (0.3 mmol) were added to a solution of photocatalyst
Ir(ppy)2(dtbbpy)PF6 (1 mol%) in acetone (4 mL) at room temperature. The heterogenous mixture was
degassed by three cycles of freezeꢀpumpꢀthaw and then placed in the irradiation apparatus equipped
o
with a 25 W blue lightꢀemitting diode (LED) strip. The resulting mixture was stirred at 20 C until the
starting material was completely consumed after 2.5 h. Upon completion of the reaction, the reaction
mixture was evaporated under reduced pressure, and the resulting crude mixture was purified on silica
gel flash column chromatography using ethyl acetate/hexanes (1/4) eluent to give the corresponding
oxazolidine derivatives.
2ꢀmethylꢀ4ꢀphenylꢀ1ꢀtosylꢀ4,5ꢀdihydroꢀ1Hꢀimidazole (3a).8d Colorless oil; 59.9 mg, 95% yield; 1H
NMR (400 MHz, CDCl3) δ (ppm) = 2.39 (s, 3H), 2.44 (s, 3H), 3.62 (t, J = 9.5 Hz, 1H), 4.17 (t, J = 10.1
Hz, 1H), 4.98 (t, J = 9.0 Hz, 1H), 7.04 (dd, J = 6.9, 1.6 Hz, 2H), 7.21−7.28 (m, 3H), 7.34 (d, J = 8.1 Hz,
2H), 7.74 (d, J = 8.2 Hz, 2H); 13 C NMR (100 MHz, CDCl3) δ (ppm) = 16.7, 21.5, 55.4, 66.5, 126.3,
127.1, 127.5, 128.6, 130.0, 135.1, 141.5, 144.7, 156.3; IR (KBr, cmꢀ1): 3370, 3282, 3063, 2924, 1646,
1598, 1495, 1359, 1242, 1166, 1115, 1024, 969, 815, 701, 659, 593, 547. HRMS (ESI) for
C17H19N2O2S [M+H] +calcd.315.1162, found 315.1172
2ꢀmethylꢀ4ꢀphenylꢀ1ꢀ(phenylsulfonyl)ꢀ4,5ꢀdihydroꢀ1Hꢀimidazole (3b). Colorless oil; 56.4 mg, 94%
1
yield; H NMR (400 MHz, CDCl3) δ (ppm) = 2.41 (s, 3H), 3.64 (dd, J = 9.6, 8.1 Hz, 1H), 4.19 (t, J =
10.1 Hz, 1H), 5.00 (t, J = 8.8 Hz, 1H), 7.04 (dd, J = 6.9, 1.4 Hz, 2H), 7.22−7.29 (m, 3H), 7.57 (t, J =
7.7 Hz, 2H), 7.66 (t, J = 7.4 Hz, 1H), 7.74 (d, J = 7.8 Hz, 2H); 13 C NMR (100 MHz, CDCl3) δ (ppm) =
16.8, 55.5, 66.6, 126.3, 127.1, 127.7, 128.7, 129.5, 133.7, 138.1, 141.4, 156.2; IR (KBr, cmꢀ1): 3278,
3064, 2927, 1647, 1543, 1448, 1360, 1243, 1169, 1116, 1092, 1024, 970, 757, 730, 690, 600, 570.
HRMS (ESI) for C16H17N2O2S [M+H] +calcd.301.1005, found 301.1004.
4ꢀ(4ꢀfluorophenyl)ꢀ2ꢀmethylꢀ1ꢀtosylꢀ4,5ꢀdihydroꢀ1Hꢀimidazole (3c).17 Colorless oil; 58.5 mg, 88%
yield; 1H NMR (400 MHz, CDCl3) δ (ppm) = 2.39 (d, J = 1.4 Hz, 3H), 2.46 (s, 3H), 3.58 (dd, J = 9.8,
7.8 Hz, 1H), 4.16 (t, J = 10.1 Hz, 1H), 4.97 (t, J = 8.7 Hz, 1H), 6.94 (t, J = 8.7 Hz, 2H), 7.00−7.03 (m,
2H), 7.35 (d, J = 8.1 Hz, 2H), 7.74 (d, J = 8.3 Hz, 2H); 13 C NMR (100 MHz, CDCl3) δ (ppm) =16.8,
21.5, 55.5, 65.9, 115.5 (d, J = 21.3 Hz), 127.2, 128.0 (d, J = 8.1 Hz), 130.1, 137.4 (d, J = 3.1 Hz),
144.8, 156.6, 162.1 (d, J = 244.5 Hz); IR (KBr, cmꢀ1): 3283, 3060, 2927, 1646, 1599, 1511, 1360, 1225,
1166, 1114, 1092, 1016, 971, 836, 710, 657, 593, 546. HRMS (ESI) for C17H18FN2O2S [M+H]
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+calcd.333.1068, found 333.1076.
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4ꢀ(4ꢀchlorophenyl)ꢀ2ꢀmethylꢀ1ꢀtosylꢀ4,5ꢀdihydroꢀ1Hꢀimidazole (3d).17 Colorless oil; 66.0 mg, 95%
yield; 1H NMR (400 MHz, CDCl3) δ (ppm) = 2.39 (d, J = 1.4 Hz, 3H), 2.40 (s, 3H), 3.57 (dd, J = 9.8,
7.8 Hz, 1H), 4.17 (t, J = 10.1 Hz, 1H), 4.97 (t, J = 8.9 Hz, 1H), 6.98 (d, J = 8.4 Hz, 2H), 7.23 (d, J =
8.4 Hz, 2H), 7.35 (d, J = 8.1 Hz, 2H), 7.73 (d, J = 8.2 Hz, 2H); 13 C NMR (100 MHz, CDCl3) δ (ppm)
=16.8, 21.6, 55.4, 65.8, 127.2, 127.7, 128.8, 130.1, 133.4, 135.0, 140.1, 144.9, 156.9; IR (KBr, cmꢀ1):
3276, 3059, 2926, 1647, 1598, 1493, 1360, 1166, 1115, 1091, 1015, 971, 816, 736, 656, 593, 547.
HRMS (ESI) for C17H18ClN2O2S [M+H] +calcd.349.0772, found 349.0782.
4ꢀ(4ꢀbromophenyl)ꢀ2ꢀmethylꢀ1ꢀtosylꢀ4,5ꢀdihydroꢀ1Hꢀimidazole (3e).17 Colorless oil; 55.7 mg, 71%
yield; 1H NMR (400 MHz, CDCl3) δ (ppm) = 2.39 (s, 3H), 2.45 (s, 3H), 3.56 (dd, J = 9.8, 7.9 Hz, 1H),
4.16 (t, J = 10.1 Hz, 1H), 4.95 (t, J = 8.7 Hz, 1H), 6.92 (d, J = 8.3 Hz, 2H), 7.32−7.38 (m, 4H), 7.72 (d,
J = 8.2 Hz, 2H); 13 C NMR (100 MHz, CDCl3) δ (ppm) =16.7, 21.5, 55.3, 65.8, 121.4, 127.1, 128.0,
130.1, 131.6, 135.0, 140.6, 144.8, 156.8; IR (KBr, cmꢀ1): 3276, 3055,2924, 1646, 1597, 1488, 1359,
1242, 1166, 1116, 1091, 1011, 971, 816, 709, 663, 593, 547. HRMS (ESI) for C17H18BrN2O2S [M+H]
+calcd.393.0267, found 393.0279.
4ꢀ(3ꢀchlorophenyl)ꢀ2ꢀmethylꢀ1ꢀtosylꢀ4,5ꢀdihydroꢀ1Hꢀimidazole (3f).8d Colorless oil; 58.0 mg, 83%
yield; 1H NMR (400 MHz, CDCl3) δ (ppm) = 2.40 (d, J = 1.3 Hz, 3H), 2.45 (s, 3H), 3.57 (dd, J = 9.9,
7.7 Hz, 1H), 4.18 (t, J = 10.2 Hz, 1H), 4.96 (t, J = 9.0 Hz, 1H), 6.94ꢀ6.97 (m, 2H), 7.20 (d, J = 5.2 Hz,
2H), 7.34 (d, J = 8.2 Hz, 2H), 7.73 (d, J = 8.2 Hz, 2H); 13 C NMR (100 MHz, CDCl3) δ (ppm) =16.8,
21.6, 55.2, 66.0, 124.6, 126.4, 127.1, 127.7, 129.9, 130.1, 134.5, 134.9, 143.7, 144.9, 156.9; IR (KBr,
cmꢀ1): 3381, 3062, 2927, 1645, 1597, 1360, 1242, 1167, 1116, 1025, 787, 657, 593, 546. HRMS (ESI)
for C17H18ClN2O2S [M+H] +calcd.349.0772, found 349.0771.
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4ꢀ(2ꢀchlorophenyl)ꢀ2ꢀmethylꢀ1ꢀtosylꢀ4,5ꢀdihydroꢀ1Hꢀimidazole (3g).8d Colorless oil; 61.1 mg, 88%
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yield; H NMR (400 MHz, CDCl3) δ (ppm) = 2.43 (s, 6H), 3.53 (dd, J = 9.9, 7.7 Hz, 1H), 4.30 (t, J =
10.2 Hz, 1H), 5.31 (t, J = 8.6 Hz, 1H), 7.08−7.10 (m, 1H), 7.13−7.21 (m, 2H), 7.30−7.34 (m, 3H), 7.72
(d, J = 8.3 Hz, 2H); 13 C NMR (100 MHz, CDCl3) δ (ppm) =16.9, 21.5, 54.7, 63.7, 127.0, 127.1, 127.4,
128.6, 129.3, 130.0, 132.2, 135.2, 139.5, 144.7, 157.4; IR (KBr, cmꢀ1): 3379, 3064, 2924, 1648, 1473,
1437, 1360, 1244, 1186, 1118, 1092, 1030, 970, 815, 756, 731, 657, 593, 546. HRMS (ESI) for
C17H18ClN2O2S [M+H] +calcd.349.0772, found 349.0770.
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2ꢀmethylꢀ4ꢀ(pꢀtolyl)ꢀ1ꢀtosylꢀ4,5ꢀdihydroꢀ1Hꢀimidazole (3h).8b, 8d Colorless oil; 56.7 mg, 86% yield; H
NMR (400 MHz, CDCl3) δ (ppm) = 2.94 (s, 3H), 2.37 (d, J = 1.5 Hz, 3H), 2.45 (s, 3H), 3.60 (dd, J =
9.8, 8.0 Hz, 1H), 4.14 (t, J = 10.0 Hz, 1H), 4.94 (t, J = 8.6 Hz, 1H), 6.92 (d, J = 8.0 Hz, 2H), 7.06 (d, J
= 7.9 Hz, 2H), 7.34 (d, J = 8.1 Hz, 2H), 7.73 (d, J = 8.3 Hz, 2H); 13 C NMR (100 MHz, CDCl3) δ (ppm)
=16.7, 21.0, 21.5, 55.5, 66.3, 126.2, 127.1, 129.2, 130.0, 135.1, 137.2, 138.5, 144.6, 156.1; IR (KBr,
cmꢀ1): 3279, 3027, 2923, 1647, 1597, 1515, 1432, 1358, 1241, 1166, 1116, 1091, 1020, 969, 816, 711,
657, 594, 546. HRMS (ESI) for C18H21N2O2S [M+H] +calcd.329.1318, found 329.1315.
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2ꢀmethylꢀ4ꢀ(mꢀtolyl)ꢀ1ꢀtosylꢀ4,5ꢀdihydroꢀ1Hꢀimidazole (3i).8d Colorless oil; 58.9 mg, 90% yield; H
NMR (400 MHz, CDCl3) δ (ppm) = 2.56 (s, 3H), 2.39 (s, 3H), 2.45 (s, 3H), 3.62 (dd, J = 9.6, 8.1 Hz,
1H), 4.16 (t, J = 10.1 Hz, 1H), 4.95 (t, J = 9.0 Hz, 1H), 6.80 (s, 1H), 6.84 (d, J = 7.6 Hz, 1H), 7.04 (d, J
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= 7.5 Hz, 1H), 7.14 (t, J = 7.5 Hz, 1H), 7.34 (d, J = 8.1 Hz, 2H), 7.75 (d, J = 8.2 Hz, 2H); 13 C NMR
(100 MHz, CDCl3) δ (ppm) = 16.8, 21.1, 21.5, 55.4, 66.5, 123.4, 126.9, 127.2, 128.3, 128.5, 130.0,
135.1, 138.3, 141.4, 144.6, 156.2; IR (KBr, cmꢀ1): 3281, 2923, 1646, 1597, 1431, 1359, 1167, 1114,
1092, 1024, 815, 788, 710, 659, 594, 546. HRMS (ESI) for C18H21N2O2S [M+H] +calcd.329.1318,
found 329.1326.
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2ꢀmethylꢀ4ꢀ(oꢀtolyl)ꢀ1ꢀtosylꢀ4,5ꢀdihydroꢀ1Hꢀimidazole (3j). 8d Colorless oil; 64.0 mg, 97% yield; H
NMR (400 MHz, CDCl3) δ (ppm) = 2.27 (s, 3H), 2.42 (d, J = 1.4 Hz, 3H), 2.45 (s, 3H), 3.49 (dd, J =
9.4, 8.2 Hz, 1H), 4.22 (t, J = 10.0 Hz, 1H), 5.18 (t, J = 9.2 Hz, 1H), 6.92 (d, J = 7.5 Hz, 1H), 7.06−7.10
(m, 1H), 7.11−7.14 (m, 2H), 7.33 (d, J = 8.0 Hz, 2H), 7.33 (d, J = 8.3 Hz, 2H); 13 C NMR (100 MHz,
CDCl3) δ (ppm) = 16.9, 19.4, 21.6, 54.9, 63.5, 125.7, 126.4, 127.2, 127.3, 130.1, 130.3, 134.5, 135.3,
140.0, 144.7, 156.5; IR (KBr, cmꢀ1): 3278, 3060, 2928, 1649, 1597, 1510, 1461, 1359, 1271, 1167,
1117, 1091, 968, 815, 758, 711, 658, 594, 545. HRMS (ESI) for C18H21N2O2S [M+H] +calcd.329.1318,
found 329.1315.
4ꢀ(4ꢀ(tertꢀbutyl)phenyl)ꢀ2ꢀmethylꢀ1ꢀtosylꢀ4,5ꢀdihydroꢀ1Hꢀimidazole (3k). Colorless oil; 62.2 mg, 84%
yield; 1H NMR (400 MHz, CDCl3) δ (ppm) = 2.28 (s, 9H), 2.37 (d, J = 1.4 Hz, 3H), 2.45 (s, 3H), 3.65
(dd, J = 9.7, 8.0 Hz, 1H), 4.14 (t, J = 10.0 Hz, 1H), 4,95 (t, J = 8.7 Hz, 1H), 6.97 (d, J = 8.3 Hz, 2H),
7.27 (d, J = 8.3 Hz, 2H), 7.35 (d, J = 8.2 Hz, 2H), 7.75 (d, J = 8.3 Hz, 2H); 13 C NMR (100 MHz,
CDCl3) δ (ppm) = 16.7, 21.5, 31.2, 34.4, 55.3, 66.2, 125.5, 126.0, 127.2, 130.0, 135.2, 138.4, 144.6,
150.5, 156.0; IR (KBr, cmꢀ1): 3055, 2962, 1647, 1598, 1510, 1474, 1360, 1242, 1167, 1112, 1019, 971,
815, 656, 594, 546. HRMS (ESI) for C21H27N2O2S [M+H] +calcd.371.1788, found 371.1786.
2ꢀmethylꢀ1ꢀtosylꢀ1,3a,8,8aꢀtetrahydroindeno[1,2ꢀd]imidazole (3l). White solid; 52.1 mg, 80% yield; 1H
NMR (400 MHz, CDCl3) δ (ppm) = 2.25 (s, 3H), 2.46 (s, 3H), 3.43−3.57 (m, 2H), 4.83 (t, J = 6.7 Hz,
1H), 5.42 (d, J = 8.7 Hz, 1H), 7.24−7.27 (m, 3H), 7.37 (d, J = 8.0 Hz, 2H), 7.46 (d, J = 7.2 Hz, 1H),
7.78 (d, J = 8.2 Hz, 2H); 13 C NMR (100 MHz, CDCl3) δ (ppm) = 16.8, 21.6, 41.2, 63.7, 74.7, 125.1,
125.3, 127.2, 127.4, 128.6, 130.1, 135.9, 139.8, 140.7, 144.8, 156.3; IR (KBr, cmꢀ1): 3028, 2927, 1716,
1646, 1598, 1434, 1358, 1235, 1165, 1092, 1014, 966, 913, 814, 754, 691, 595, 545. HRMS (ESI) for
C18H19N2O2S [M+H] +calcd.327.1162, found 327.1164.
2ꢀmethylꢀ3ꢀtosylꢀ3a,4,5,9bꢀtetrahydroꢀ3Hꢀnaphtho[1,2ꢀd]imidazole (3m).8b Colorless oil; 57.8 mg, 85%
yield; 1H NMR (400 MHz, CDCl3) δ (ppm) = 2.00−2.15 (m, 2H), 2.29 (d, J = 1.8 Hz, 3H), 2.45 (s, 3H),
2.55−2.62 (m, 1H), 2.70−2.76 (m, 1H), 4.43−4.48 (m, 1H), 4,85 (d, J = 9.5 Hz, 1H), 7.08 (d, J = 7.3 Hz,
1H), 7.14−7.23 (m, 2H), 7.36 (d, J = 8.0 Hz, 2H), 7.43 (d, J = 7.4 Hz, 1H), 7.78 (d, J = 8.3 Hz, 2H); 13
C NMR (100 MHz, CDCl3) δ (ppm) = 17.1, 21.5, 25.8, 28.5, 60.6, 65.6, 126.8, 126.9, 127.2, 128.1,
129.6, 130.1, 133.8, 136.6, 137.7, 144.5, 155.5; IR (KBr, cmꢀ1): 3278, 3062, 2929, 1647, 1598, 1494,
1454, 1356, 1244, 1164, 1096, 1021, 911, 814, 734, 664, 602, 546. HRMS (ESI) for C19H21N2O2S
[M+H] +calcd.341.1318, found 341.1322.
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2,4ꢀdimethylꢀ4ꢀphenylꢀ1ꢀtosylꢀ4,5ꢀdihydroꢀ1Hꢀimidazole (3n). Colorless oil; 58.3 mg, 89% yield; H
NMR (400 MHz, CDCl3) δ (ppm) = 1.46 (s, 3H), 2.37 (s, 3H), 2.41 (s, 3H), 3.79 (d, J = 9.6 Hz, 1H),
3.91 (d, J = 9.6 Hz, 1H), 7.20−7.30 (m, 7H), 7.70 (d, J = 8.2 Hz, 2H); 13 C NMR (100 MHz, CDCl3) δ
(ppm) = 16.8, 21.5, 29.5, 61.0, 69.5, 124.9, 126.8, 127.0, 128.4, 130.0, 135.3, 144.5, 146.3, 154.1; IR
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(KBr, cmꢀ1): 3282, 2969, 2926, 1647, 1447, 1358, 1167, 1090, 1041, 924, 815, 765, 717, 664, 593, 545.
HRMS (ESI) for C18H21N2O2S [M+H] +calcd.329.1318, found 329.1322.
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4ꢀ(3ꢀchlorophenyl)ꢀ2,4ꢀdimethylꢀ1ꢀtosylꢀ4,5ꢀdihydroꢀ1Hꢀimidazole (3o). Colorless oil; 66.6 mg, 92%
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yield; H NMR (400 MHz, CDCl3) δ (ppm) = 1.45 (s, 3H), 2.38 (s, 3H), 2.42 (s, 3H), 3.74 (d, J = 9.8
Hz, 1H), 3.89 (d, J = 9.8 Hz, 1H), 7.09−7.11 (m, 1H), 7.16−7.22 (m, 3H), 7.30 (d, J = 8.1 Hz, 2H), 7.69
(d, J = 8.2 Hz, 2H); 13 C NMR (100 MHz, CDCl3) δ (ppm) = 16.9, 21.5, 29.4, 60.9, 69.3, 123.2, 125.5,
127.0, 129.7, 130.0, 134.3, 135.1, 144.7, 148.5, 154.7; IR (KBr, cmꢀ1): 3367, 2973, 2926, 1736, 1648,
1597, 1475, 1359, 1283, 1168, 1118, 1041, 1010, 925, 814, 743, 696, 660, 594, 546. HRMS (ESI) for
C18H20ClN2O2S [M+H] +calcd.363.0929, found 363.0926.
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2ꢀethylꢀ4ꢀphenylꢀ1ꢀtosylꢀ4,5ꢀdihydroꢀ1Hꢀimidazole (3p).18 Colorless oil; 62.2 mg, 95% yield; H NMR
(400 MHz, CDCl3) δ (ppm) = 1.29 (t, J = 7.4 Hz, 3H), 2.44 (s, 3H), 2.77 (m, 2H), 3.61 (dd, J = 9.8, 7.8
Hz, 1H), 4.17 (t, J = 10.1 Hz, 1H), 4.99 (dd, J = 9.9, 8.0 Hz, 1H), 7.02−7.04 (m, 2H), 7.22−7.27 (m,
3H), 7.33 (d, J = 8.0 Hz, 2H), 7.73 (d, J = 8.2 Hz, 2H); 13 C NMR (100 MHz, CDCl3) δ (ppm) = 11.0,
21.5, 23.3, 55.8, 66.6, 126.3, 127.2, 127.5, 128.6, 130.0, 135.3, 141.8, 144.6, 160.8; IR (KBr, cmꢀ1):
3296, 3030, 2925, 1736, 1637, 1598, 1494, 1471, 1401, 1359, 1244, 1162, 1097, 994, 815, 701, 660,
587, 567. HRMS (ESI) for C18H21N2O2S [M+H] +calcd.329.1318, found 329.1315.
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2ꢀcyclopropylꢀ4ꢀphenylꢀ1ꢀtosylꢀ4,5ꢀdihydroꢀ1Hꢀimidazole (3q). Colorless oil; 58.0 mg, 85% yield; H
NMR (400 MHz, CDCl3) δ (ppm) = 0.97−1.12 (m, 4H), 2.42−2.50 (m, 4H), 3.60 (dd, J = 10.1, 7.4 Hz,
1H), 4.19 (t, J = 10.2 Hz, 1H), 4.89 (dd, J = 10.2, 7.5 Hz, 1H), 6.89−6.91 (m, 2H), 7.19−7.21 (m, 3H),
7.29 (d, J = 8.1 Hz, 2H), 7.79 (d, J = 8.2 Hz, 2H); 13 C NMR (100 MHz, CDCl3) δ (ppm) = 8.6, 9.7,
10.4, 21.5, 56.4, 65.9, 126.2, 127.3, 127.4, 128.5, 129..9, 135.0, 142.1, 144.5, 161.7; IR (KBr, cmꢀ1):
3290, 2980, 2931, 1736, 1647, 1535, 1454, 1331, 1243, 1161, 1094, 913, 815, 701, 663, 590, 549.
HRMS (ESI) for C19H21N2O2S [M+H] +calcd.341.1318, found 341.1315.
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2,4ꢀdiphenylꢀ1ꢀtosylꢀ4,5ꢀdihydroꢀ1Hꢀimidazole (3r).8b, 8d Colorless oil; 16.4 mg, 22% yield; H NMR
(400 MHz, CDCl3) δ (ppm) = 2.42 (s, 3H), 3.86 (dd, J = 11.4, 8.1 Hz, 1H), 4.43 (dd, J = 11.3, 10.2 Hz,
1H), 4.99 (dd, J = 9.8, 8.3 Hz, 1H), 6.96−6.98 (m, 2H), 7.18−7.22 (m, 5H), 7.39−7.45 (m, 4H), 7.52 (t,
J = 7.4 Hz, 1H), 7.77 (d, J = 7.2 Hz, 2H); 13 C NMR (100 MHz, CDCl3) δ (ppm) = 21.6, 56.9, 67.9,
126.3, 127.4, 127.6, 127.7, 128.6, 129.7, 129.8, 130.2, 131.1, 134.5, 141.5, 144.6, 159.8; IR (KBr,
cmꢀ1): 3062, 2924, 1628, 1598, 1509, 1449, 1365, 1169, 1089, 1023, 911, 815, 732, 698, 663, 605, 546.
HRMS (ESI) for C22H21N2O2S [M+H] +calcd.377.1318, found 377.1316.
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2,2ꢀdimethylꢀ5ꢀphenylꢀ3ꢀtosyloxazolidine (4a).8a, 8b White solid; 58.3 mg, 88% yield; mp 89−91 oC; H
NMR (400 MHz, CDCl3) δ (ppm) = 1.68 (s, 3H), 1.74 (s, 3H), 2.42 (s, 3H), 3.14 (t, J = 9.1 Hz, 1H),
3.87 (dd, J = 8.7, 5.7 Hz, 1H), 5.10 (dd, J = 9.5, 5.7 Hz, 1H), 7.28−7.35 (m, 7H), 7.75 (d, J = 8.3 Hz,
2H); 13 C NMR (100 MHz, CDCl3) δ (ppm) = 21.5, 27.0, 27.5, 54.0, 76.2, 97.3, 126.2, 127.3, 128.5,
128.5, 129.6, 137.3, 137.4, 143.4; IR (KBr, cmꢀ1): 3033, 2985, 2878, 1737, 1599, 1496, 1370, 1344,
1245, 1218, 1155, 1095, 1060, 1028, 955, 816, 759, 709, 659, 593, 548. HRMS (ESI) for C18H22NO3S
[M+H] +calcd.332.1315, found 332.1314.
2,2ꢀdimethylꢀ5ꢀ(pꢀtolyl)ꢀ3ꢀtosyloxazolidine (4b).19 White solid; 38.6 mg, 56% yield; mp 120−122 oC; 1H
NMR (400 MHz, CDCl3) δ (ppm) = 1.68 (s, 3H), 1.73 (s, 3H), 2.33 (s, 3H), 2.42 (s, 3H), 3.14 (t, J =
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9.1 Hz, 1H), 3.85 (dd, J = 8.7, 5.7 Hz, 1H), 5.08 (dd, J = 9.4, 5.6 Hz, 1H), 7.14 (d, J = 8.0 Hz, 2H),
7.20 (d, J = 8.1 Hz, 2H), 7.30 (d, J = 8.0 Hz, 2H), 7.76 (d, J = 8.1 Hz, 2H); 13 C NMR (100 MHz,
CDCl3) δ (ppm) = 21.1, 21.4, 27.1, 27.5, 54.0, 76.1, 97.2, 126.1, 127.3, 129.2, 129.6, 134.3, 137.3,
138.3, 143.3; IR (KBr, cmꢀ1): 3363, 2923, 2852, 1737, 1657, 1598, 1459, 1371, 1343, 1244, 1154, 1094,
954, 813, 687, 653, 592, 547. HRMS (ESI) for C19H24NO3S [M+H] +calcd.346.1471, found 346.1470.
5ꢀ(4ꢀisopropylphenyl)ꢀ2,2ꢀdimethylꢀ3ꢀtosyloxazolidine (4c). White solid; 43.4 mg, 58% yield; mp
102−103 oC; 1H NMR (400 MHz, CDCl3) δ (ppm) = 1.21 (d, J = 6.9 Hz, 6H), 1.67 (s, 3H), 1.72 (s, 3H),
2.42 (s, 3H), 2,83−2.93 (m, 1H), 3.16 (t, J = 9.1 Hz, 1H), 3.84 (dd, J = 8.7, 5.7 Hz, 1H), 5.07 (dd, J =
9.5, 5.6 Hz, 1H), 7.17−7.24 (m, 4H), 7.29 (d, J = 8.0 Hz, 2H), 7.75 (d, J = 8.0 Hz, 2H); 13 C NMR (100
MHz, CDCl3) δ (ppm) = 21.4, 23.8, 23.9, 27.0, 27.5, 33.8, 76.1, 97.2, 126.3, 126.6, 127.3, 129.6, 134.6,
137.3, 143.3, 149.4; IR (KBr, cmꢀ1): 2961, 2872, 1738, 1599, 1461, 1371, 1345, 1244, 1156, 1094, 956,
828, 687, 654, 593, 549. HRMS (ESI) for C21H28NO3S [M+H] +calcd.374.1784, found 374.1782.
5ꢀ(4ꢀ(tertꢀbutyl)phenyl)ꢀ2,2ꢀdimethylꢀ3ꢀtosyloxazolidine (4d). White solid; 51.2 mg, 66% yield; mp
99−100 oC; 1H NMR (400 MHz, CDCl3) δ (ppm) = 1.29 (s, 9H), 1.67 (s, 3H), 1.73 (s, 3H), 2.42 (s, 3H),
3.16 (t, dd, J = 9.1 Hz, 1H), 3.85 (dd, J = 8.7, 5.6 Hz, 1H), 5.08 (dd, J = 9.5, 5.7 Hz, 1H), 7.24 (d, J =
8.3 Hz, 2H), 7.29 (d, J = 8.2 Hz, 2H), 7.35 (d, J = 8.3 Hz, 2H), 7.75 (d, J = 8.2 Hz, 2H); 13 C NMR (100
MHz, CDCl3) δ (ppm) = 21.4, 27.0, 27.5, 31.2, 34.5, 53.8, 76.1, 97.2, 125.5, 126.0, 127.3, 129.6, 134.2,
137.3, 143.3, 151.6; IR (KBr, cmꢀ1): 2961, 1738, 1599, 1461, 1345, 1245, 1222, 1156, 1094, 1015, 956,
826, 711, 684, 653, 593, 549. HRMS (ESI) for C22H30NO3S [M+H] +calcd.388.1941, found 388.1940.
5ꢀ(4ꢀfluorophenyl)ꢀ2,2ꢀdimethylꢀ3ꢀtosyloxazolidine (4e). White solid; 42.0 mg, 60% yield; mp 91−93
oC; 1H NMR (400 MHz, CDCl3) δ (ppm) = 1.68 (s, 3H), 1.72 (s, 3H), 2.42 (s, 3H), 3.11 (t, J = 9.1 Hz,
1H), 3.84 (dd, J = 8.7, 5.7 Hz, 1H), 5.07 (dd, J = 9.4, 5.7 Hz, 1H), 7.01 (t, J = 8.6 Hz, 2H), 7.26−7.31
(m, 4H), 7.75 (d, J = 8.2 Hz, 2H); 13 C NMR (100 MHz, CDCl3) δ (ppm) = 21.5, 27.1, 27.4, 54.0, 75.6,
97.3, 115.5 (J = 21.7 Hz), 127.3, 128.0 (J = 8.1 Hz), 129.6, 133.2 (J = 3.0 Hz), 137.2, 143.5, 162.7 (J =
245.6 Hz); IR (KBr, cmꢀ1): 2985, 2929, 1606, 1513, 1459, 1370, 1342, 1225, 1153, 1093, 1014, 956,
835, 710, 688, 654, 592. HRMS (ESI) for C18H21FNO3S [M+H] +calcd.350.1221, found 350.1219.
5ꢀ(4ꢀchlorophenyl)ꢀ2,2ꢀdimethylꢀ3ꢀtosyloxazolidine (4f).19 White solid; 34.2 mg, 47% yield; mp
112−114 oC; 1H NMR (400 MHz, CDCl3) δ (ppm) = 1.67 (s, 3H), 1.72 (s, 3H), 2.42 (s, 3H), 3.09 (t, J =
9.1 Hz, 1H), 3.85 (dd, J = 8.8, 5.8 Hz, 1H), 5.07 (dd, J = 9.3, 5.7 Hz, 1H), 7.22−7.31 (m, 6H), 7.74 (d,
J = 8.3 Hz, 2H); 13 C NMR (100 MHz, CDCl3) δ (ppm) = 21.5, 27.0, 27.4, 53.5, 75.5, 97.4, 127.3,
127.5, 128.7, 129.6, 134.2, 136.1, 137.2, 143.5; IR (KBr, cmꢀ1): 3376, 2925, 1736, 1598, 1509, 1459,
1342, 1245, 1154, 1092, 1015, 955, 817, 682, 592. HRMS (ESI) for C18H21ClNO3S [M+H]
+calcd.366.0925, found 366.0926.
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5ꢀ(4ꢀbromophenyl)ꢀ2,2ꢀdimethylꢀ3ꢀtosyloxazolidine (4g). White solid; 40.0 mg, 49% yield; mp
100−102 oC; 1H NMR (400 MHz, CDCl3) δ (ppm) = 1.67 (s, 3H), 1.72 (s, 3H), 2.42 (s, 3H), 3.09 (t, J =
9.0 Hz, 1H), 3.86 (dd, J = 8.7, 5.8 Hz, 1H), 5.06 (dd, J = 9.2, 5.7 Hz, 1H), 7.17 (d, J = 8.4 Hz, 2H),
7.30 (d, J = 8.0 Hz, 2H), 7.45 (d, J = 8.4 Hz, 2H), 7.74 (d, J = 8.3 Hz, 2H); 13 C NMR (100 MHz,
CDCl3) δ (ppm) = 21.5, 27.0, 27.4, 53.8, 75.5, 97.4, 122.3, 127.3, 127.8, 129.6, 131.7, 136.6, 137.1,
143.5; IR (KBr, cmꢀ1): 2984, 2931, 1736, 1597, 1489, 1343, 1246, 1217, 1156, 1093, 1012, 817, 676,
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592, 551. HRMS (ESI) for C18H21BrNO3S [M+H] +calcd.410.0420, found 410.0418.
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2,2ꢀdimethylꢀ3ꢀtosylꢀ3,3a,4,8bꢀtetrahydroꢀ2Hꢀindeno[2,1ꢀd]oxazole (4h). White solid; 34.2 mg, 50%
yield; mp 111−112 oC; 1H NMR (400 MHz, CDCl3) δ (ppm) = 1.60 (s, 3H), 1.64 (s, 3H), 2.44 (s, 3H),
3.05−3.20 (m, 2H), 4.58−4.63 (m, 1H), 5.45 (d, J = 6.5 Hz, 1H), 7.15 (d, J = 7.5 Hz, 1H), 7.23 (d, J =
7.1 Hz, 1H), 7.28−7.33 (m, 3H), 7.39 (d, J = 7.4 Hz, 1H), 7.81 (d, J = 8.3 Hz, 2H); 13 C NMR (100
MHz, CDCl3) δ (ppm) = 21.5, 25.8, 29.2, 39.7, 62.2, 83.1, 100.5, 125.2, 125.4, 127.2, 127.6, 129.6,
129.8, 138.2, 138.6, 142.3, 143.5; IR (KBr, cmꢀ1): 3370, 2984, 2927, 1737, 1599, 1462, 1370, 1338,
1245, 1210, 1152, 1093, 1014, 956, 753, 585, 552. HRMS (ESI) for C19H21NO3SNa [M+Na]
+calcd.366.1134, found 366.1133.
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2,2ꢀdimethylꢀ3ꢀtosylꢀ2,3,3a,4,5,9bꢀhexahydronaphtho[2,1ꢀd]oxazole (4i). White solid; 33.0 mg, 46%
yield; mp 121−123 oC; 1H NMR (400 MHz, CDCl3) δ (ppm) = 1.67 (s, 3H), 1.73 (s, 3H), 1.78−1.88 (m,
1H), 2.02−2.09 (m, 1H), 2.43 (s, 3H), 2.58−2.67 (m, 1H), 2.76−2.82 (m, 1H), 3.95−4.00 (m, 1H), 4.83
(d, J = 5.5 Hz, 1H), 7.13 (d, J = 6.9 Hz, 1H), 7.18−7.25 (m, 2H), 7.30 (d, J = 8.2 Hz, 3H), 7.82 (d, J =
8.3 Hz, 2H); 13 C NMR (100 MHz, CDCl3) δ (ppm) = 21.5, 25.5, 27.3, 27.7, 30.1, 58.5, 73.1, 97.0,
126.4, 127.4, 128.4, 128.5, 129.6, 130.2, 131.9, 137.8, 138.7, 143.3; IR (KBr, cmꢀ1): 3372, 2931, 2870,
1737, 1599, 1495, 1458, 1341, 1241, 1224, 1150, 1108, 1027, 984, 751, 664, 551. HRMS (ESI) for
C20H23NO3SNa [M+Na] +calcd.380.1291, found 380.1289.
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2,2,5ꢀtrimethylꢀ5ꢀphenylꢀ3ꢀtosyloxazolidine (4j). Colorless oil; 57.3 mg, 83% yield; H NMR (400
MHz, CDCl3) δ (ppm) = 1.46 (s, 3H), 1.54 (s, 3H), 1.74 (s, 3H), 2.39 (s, 3H), 3.65−3.71 (m, 2H),
7.22−7.31 (m, 7H), 7.67 (d, J = 8.2 Hz, 2H); 13 C NMR (100 MHz, CDCl3) δ (ppm) = 21.4, 27.4, 28.8,
29.1, 57.6, 81.2, 97.2, 124.6, 127.1, 127.3, 128.2, 129.4, 137.1, 143.4, 145.0; IR (KBr, cmꢀ1): 3379,
2982, 2932, 1737, 1599, 1447, 1346, 1245, 1162, 1090, 1028, 701, 662, 594, 549. HRMS (ESI) for
C19H23NO3SNa [M+Na] +calcd.368.1291, found 368.1290.
5ꢀ(3ꢀchlorophenyl)ꢀ2,2,5ꢀtrimethylꢀ3ꢀtosyloxazolidine (4k). Colorless oil; 66.6 mg, 88% yield; 1H NMR
(400 MHz, CDCl3) δ (ppm) = 1.48 (s, 3H), 1.51 (s, 3H), 1.72 (s, 3H), 2.40 (s, 3H), 3.65 (s, 2H),
7.16−7.27 (m, 6H), 7.66 (d, J = 8.1 Hz, 2H); 13 C NMR (100 MHz, CDCl3) δ (ppm) = 21.4, 27.3, 28.7,
28.9, 57.3, 80.7, 97.3, 122.9, 124.9, 127.3, 129.5, 129.6, 134.2, 136.9, 143.5, 147.2; IR (KBr, cmꢀ1):
2983, 2932, 1737, 1598, 1473, 1414, 1372, 1347, 1244, 1091, 996, 906, 790, 684, 594, 549. HRMS
(ESI) for C19H22ClNO3SNa [M+Na] +calcd.402.0901, found 402.0902.
AUTHOR INFORMATION
Corresponding Author
* Eꢀmail: xupf@lzu.edu.cn.
Notes
The authors declare no competing financial interest.
ACKNOWLEDGEMENTS
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We are grateful to the NSFC (21172097, 21202070, 21302075 and 21372105), the International S&T
Cooperation Program of China (2013DFR70580), and the “111”program from the MOE of P. R. China
for financial support.
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Supporting Information
9
Devices for the photocatalytic reactions, nOe spectra of 3l, 4h, and Xꢀray crystallographic data of 4i,
1H and 13C NMR spectra of the products. This material is available free of charge via the Internet at
http://pubs.acs.org.
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