Gold-Catalyzed Concomitant [3 + 3] Cycloaddition/Cascade Heterocyclization of Enynones/Enynals with Azides Leading to Furanotriazines

Article abstract of DOI:10.1021/acs.joc.5b02567

[Au]-catalyzed [3 + 3] cycloaddition reaction of enynones/enynals with azides, which allows the efficient regioselective synthesis of highly fused furo[3,4-d][1,2,3]triazines in good-to-excellent yields under mild conditions, has been developed. The synth

Full text of DOI:10.1021/acs.joc.5b02567

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Article
Gold Catalyzed Concomitant [3+3] Cycloaddition/ Cascade Heterocyclization
of Enynones/Enynals with Azides Leading to Furanotriazines
A. Leela Siva Kumari, and K. C. Kumara Swamy
J. Org. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.joc.5b02567 • Publication Date (Web): 15 Jan 2016
Downloaded from http://pubs.acs.org on February 4, 2016
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Gold Catalyzed Concomitant [3+3] Cycloaddition/ Cascade Heterocyclization of
Enynones/Enynals with Azides Leading to Furanotriazines
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A. Leela Siva Kumari and K. C. Kumara Swamy*
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School of Chemistry, University of Hyderabad, Hyderabad -500 046, Telangana, India.
E-mail: kckssc@yahoo.com; kckssc@uohyd.ac.in.
RECEIVED DATE (to be automatically inserted after your manuscript is accepted if
required according to the journal that you are submitting your paper to)
Abstract
[Au]-catalyzed [3+3] cycloaddition reaction of enynones/enynals with azides, which allows the
efficient regioselective synthesis of highly fused furo[3,4-d][1,2,3]triazines in good to excellent
yields under mild conditions has been developed. The synthetic utility of furanotriazines was
exploited by oxidation with cerium ammonium nitrate (CAN) affording highly functionalized
dihydrotriazines. Both furo[3,4-d][1,2,3]triazines and dihydrotriazines exhibit good fluorescence
activity.
Introduction
Gold catalysis has now become a powerful synthetic tool thanks to the unique ability of
gold(I) to activate carbon-carbon π-systems generating highly complex molecules from simple
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precursors.1 Construction of polysubstituted furans via gold catalysis2 has attracted considerable
attention due to the occurrence of furan skeleton in numerous natural products and
pharmaceutical ingredients in addition to their importance as building blocks in organic
synthesis.3 Enynones/ enynals, with their multifunctional nature, are versatile synthons for
transition metal (including gold) catalyzed transformations as illustrated in Scheme 1.4
Subsequent to the report by Larock et al in 2004 on gold catalyzed cyclization of enynones to
polysubstituted furans,2a-b numerous other reports via [Cu],5a-c [Ag],5d [Pd],4b, 6a-c [Pt],6d-e and
[Rh],4d catalyzed annulations as well as electrophilic cyclization6f-g have appeared in the
literature. Gold catalyzed [3+2] cycloaddition of enynones with diarylethenes is also reported.4e
Pioneering studies by J. Zhang’s group demonstrated the versatility of enynones in [3+3],4a, 7a
[3+2],4d, 7b and [4+3]4c, 8 cycloaddition reactions with various nucleophiles, although [3+3]
cycloaddition reactions are rather rare. Gold-catalyzed tandem cyclization of 1,2-bis(alkynyl)-2-
en-1-ones with indoles leading to indole-fused polycyclics is also reported recently.9 An
interesting recent work involves aza annulation of enynal azides leading to substituted
pyridines.10 Interestingly, though, phosphorus(III) azides exhibit a different mode of reaction
with DMAD (dimethyl acetylenedicarboxylate).11a-b The azide-alkyne click reaction leading to
1,2,3-triazoles is well-known; however, additional approaches by using azides and aldehydes are
also reported.11c Very recently, Luo, Xu and co-workers reported the synthesis of highly
functionalized triazines from azides with cyclopropane 1,1-diesters, wherein the cyclopropane
ring acts as an alkene equivalent.11d Among the three possible triazines systems, 1,2,3-triazines
are pharmaceutically useful because of their potent efficacy and minimal side effects.12 Hence
there are a reasonable number of reports on the synthesis and utility of 1,2,3-triazines.13 To our
knowledge, furan fused triazine (furanotriazine) ring system has never been reported till now.
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Herein, we report a novel approach to this class of compounds from the regioselective [3+3]
cycloaddition of enynones/enynals with azides via gold-catalysis.
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Scheme 1. Representative Cycloaddition Reactions of Enynones with Nucleophiles
Results and Discussion
(i). Gold catalyzed reaction of enynones 1a-m with benzyl azides/alkyl azides/ cinnamyl azides
The enynones 1a-m and the azides 2a-k used in the present study are shown in Chart 1.
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Chart 1. Enynones 1a-m and azides 2a-k
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Initially, the reaction of (E)-2-benzylidene-1,4-diphenylbut-3-yn-1-one 1a with benzyl
azide 2a in the presence of Ph3PAuCl/AgOTf (5 mol %) in dichloromethane (DCM) for 5 h led
to the [3+3] cycloadduct 3aa in 35% yield (Table 1, entry 1). The product yield marginally
improved by changing the solvent from DCM to DCE (entry 2). Varying the counter-ion or use
of IPrAuCl/AgSbF6 did not enhance the yield of 3aa (entries 3-6). IPrAuCl itself was not
effective (entry 7). Other gold catalysts like NaAuCl4.2H2O, AuCl, HAuCl4.3H2O and AuCl3
gave very poor yields (entries 8-11). Surprisingly, the reaction proceeded very smoothly with 5
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mol % LAu(CH3CN)SbF6 (L = [(2-biphenyl)di-tert-butylphosphine]) as the catalyst in DCE
solvent affording the product 3aa in 84% yield (entry 12). It is important to note that enynone in
DCE solvent should be added drop-wise at 0 oC to the solution of gold complex and azide; at rt,
the reaction is vigorous and reduces the product yield (entry 13). Addition of corresponding
silver salt to the above gold catalyst slightly decreases the yield of the desired product (entry 14).
Solvents such as DCM, 1,4-dioxane, toluene and CHCl3 were less effective (entries 15-18). In
methanol or DMF, enynone did not react with benzyl azide, but other byproducts were formed.2a-
b Other variations did not improve the yield (entries 19-22). Thus the optimal reaction conditions
are: 1a (1.0 equiv.), 2a (1.2 equiv) and LAu(CH3CN)SbF6 (5 mol %) in DCE (2 mL) as a solvent
from 0 oC to rt for 5 h.
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Table 1. Survey of Reaction Conditions for the [3+3] Cycloaddition of (E)-2-Benzylidene-
1,4-diphenylbut-3-yn-1-one 1a with Benzyl Azide 2aa
Entry Catalyst (5 mol %)
Solvent Yield(%)b
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Ph3PAuCl/AgOTf
Ph3PAuCl/AgOTf
Ph3PAuCl/AgSbF6
Ph3PAuCl/AgBF4
Ph3PAuCl/AgNTf2
DCM
DCE
DCE
DCE
DCE
35%
45%
43%
40%
33%
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6.
IPrAuCl/AgSbF6
DCM
DCM
DCE
DCE
DCE
DCE
DCE
DCE
20%
N.R
7.
IPrAuCl
8.
NaAuCl4.2H2O/AgOTf
AuCl/AgOTf
Trace
Trace
10%
12%
84%
65%c
76%d
56%
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HAuCl4.3H2O/AgOTf
AuCl3 /AgOTf
LAu(CH3CN)SbF6
LAu(CH3CN)SbF6
LAu(CH3CN)SbF6/AgSbF6 DCE
LAu(CH3CN)SbF6
LAu(CH3CN)SbF6
LAu(CH3CN)SbF6
LAu(CH3CN)SbF6
AgSbF6
DCM
dioxane 45%
toluene 55%
CHCl3 47%
DCE
DCE
DCE
DCE
30%d,e
Cu(OTf)2
N.R
LAu(CH3CN)SbF6
-
40%f
N.R.g
aStandard conditions: Enynone 1a (0.3 mmol), benzyl azide 2a (0.36 mmol), catalyst (5 mol %),
and solvent (2 mL), rt for 5 h unless otherwise noted. DCM = dichloromethane; DCE = 1,2-
dichloroethane, bIsolated yields. Addition of 1a at room temperature. Isolated after 12 h. 20
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d
e
f
g
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mol % AgSbF6 was used. 2.5 mol % catalyst was used. Reaction at 80 C for 2 d. L = [(2-
biphenyl)di-tert-butylphosphine]); IPr = 1,3-Bis(2,6-diisopropyl phenyl-imidazol-2-ylidene).
N.R = No reaction.
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We then explored the substrate scope of gold catalyzed [3+3] cycloaddition between
various 2-(1-alkynyl)-2-alken-1-ones and benzyl azides (Scheme 2). Both electron–donating
(3ab-ac) and -withdrawing groups (3ad-af) on benzyl group of azide gave decent yields, but
electron withdrawing groups (–NO2, -Br) marginally reduced the yield. Dihalo substituted azide
(2e) also produced the desired product 3ae in good yield. The generality of this method could be
extended to octyl (2g), as well as cinnamyl azides like (2h) and (2i) affording 3ag, 3ah and 3ai
in 86%, 72%, and 72% yields respectively. Secondary azide [(1-azidoethyl)benzene] 2j and 9-
anthracenylmethyl azide 2k also worked well offering the corresponding cycloadducts 3aj and
3ak in good yields. The reaction was very clean and the corresponding furanotriazines 3ba-ia
and 3ka-ma were obtained in 53-86% yield with high regioselectivity. This methodology also
tolerates the presence of cyclohexenyl moiety (R2) at the triple bond position resulting in
corresponding [3+3] annulation product 3ja. A limitation though is the case of phenyl azide
where multiple products were obtained; this may be due to the delocalization of electron density
on azide nitrogen to the benzene ring. The structure of annulation product 3aa was confirmed by
single crystal X-ray diffraction (Figure S1).
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Scheme 2. Scope of the Gold Catalyzed [3+3] Annulation Reaction of 2-(1-Alkynyl)-2-
alken-1-ones (1a-m) with Azides (2a-k)a
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aConditions: Enynone 1 (0.3 mmol), azide 2 (0.36 mmol), LAu(CH3CN)SbF6 (5 mol %), DCE (2
mL), rt for 5 h.
The absorption and fluorescence emission spectra of compounds 3ag and 3ah can be
compared with that of compound 3ak. Though compound 3ak has similar and slightly lower
absorbance than compound 3ag and 3ah respectively, it shows higher fluorescence emission
intensity as expected for an anthracenyl compound (Figure 1 and Figure-S4). Compounds 3aa,
3ab, 3ag, 3ah, 3ak and 3ca are also fluorescence active (cf. Figure 1 and Figures S3-S4). Thus
these products could be of use as good fluorescence active materials.
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Figure 1. Absorbance (A) and fluorescence emission spectra (B) of compounds 3ah and 3ak
with c = 1.71x10-2 mol/L in THF (upon excitation at 357 nm and 370 nm respectively). Quantum
yields for 3ah and 3ak are 0.0011 and 0.014, respectively
(ii) Gold catalyzed [3+3] addition of enynals with benzyl azides
In the next step, we expanded the utility of the above reaction to include enynals.
Reaction between (E)-2-benzylidene-4-phenylbut-3-ynal (4a) with benzyl azide (2a) by using the
above reaction conditions resulting in the desired [3+3] cycloadduct 5aa in 32% yield with most
of the starting material remained even after longer reaction time. Pleasingly, though, upon raising
o
the reaction temperature to 70 C compound 5aa could be obtained in 73% yield after 10 h. At
room temperature it took 48 h for completion of the reaction. In an analogous manner, reactions
using compounds 4b-e also proceeded smoothly and resulted in the corresponding [3+3]
cycloadducts 5ba-ea in good yields (Scheme 3).
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Scheme 3. Gold Catalyzed [3+3] Cycloaddition of Enynals (4a-e) with Benzyl Azide (2a-b)a
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aConditions: Enynal 4 (0.3 mmol), azide 2 (0.36 mmol), LAu(CH3CN)SbF6 (5 mol%), DCE (2
mL), 70 oC for 10 h.
(iii) Gold catalyzed (3+2) cycloaddition reaction of enynones 6 and 7a-b with benzyl azide (2a)
Interestingly, in contrast to the above, in the presence of above gold catalyst, enynones 6
and 7a-b underwent [3+2] cycloaddition with benzyl azide 2a. In these substrates, only alkene
part of the enynones reacts with benzyl azide resulting in the formal [3+2] cycloadducts 8 and
9aa-9ba, rather than the [3+3] cycloadducts, in 75%, 60% and 65% yields respectively.14 The
difference between this reaction and the one shown in Scheme 2 may be rationalized by realizing
that the R3 group is aryl in the case of 1a-k (cf. Scheme 2) for [3+3] cycloaddition and alkyl in
the case of precursors 6-7a-b for the [3+2] cycloaddition involving the alkene moiety.
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Scheme 4. [3+2] Cycloaddition of Enynones 6 and 7a-b with Benzyl Azide (2a).
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Reaction conditions: Enynone 6/7a-b (0.3 mmol), azide 2 (0.36 mmol), LAu(CH3CN)SbF6 (5
mol%), DCE (2 mL), rt for 5 h.
(iv) Synthetic utility of furanotriazines- Selective opening of furan ring leading to 1,2,3-
triazines
1,2,3-Triazines constitute an attractive class of compounds to develop new drugs in the
future, but synthetic routes to them are rarely reported.12,13 Keeping this in mind, we performed
the furan ring opening reaction of furanotriazine 3aa with cerium(IV) ammonium nitrate (CAN)
at rt/15 min that afforded the desired tetrasubstituted 1,2,3-triazine 10 in 96% yield. The
generality of this reaction was explored using furo[3,4-d][1,2,3]triazines 3ea, 3fa and 3ka. Thus
we obtained the highly functionalized 1,2,3-triazines (11-13) in excellent yields (Scheme 5). The
structure of compound 12 was further confirmed by single crystal X-ray analysis (Figure S2).
Compounds 10 and 12 are also fluorescence active (Figure S5).
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Scheme 5. Highly Substituted [1,2,3]Triazines (10-13) from Ring Opening of Furo[3,4-
d][1,2,3]triazines
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(v) Plausible pathway for the gold catalyzed cycloaddition of enynones/enynals with benzyl
azide
A plausible pathway for the above [3+3] cycloaddition involves the initial activation of
the alkyne end of enynal/enynone 1/4 with gold followed by intramolecular attack of carbonyl
oxygen leading to furanyl gold intermediate A4a, 4c-e which acts as a carbon electrophile (Scheme
6). Intermediate B is formed by nucleophilic attack of azide nitrogen on the highly activated
species A. Intermediate B undergoes intramolecular C-N bond formation to furnish the desired
[3+3] cycloadduct 3/5 with regeneration of the gold catalyst. In the formation of the [3+2]
cycloaddition products [8, 9aa, 9ba], it is likely that [AuI] is coordinated to both the triple bond
and the carbonyl oxygen with an electrophilic carbon center in the intermediate stage such as that
shown in (C).15 It is possible that the alkyl group R in 6 and 7a-b may facilitate the oxygen
coordination better than an aryl group at this position.
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Scheme 6. Plausible Pathway for the Gold Catalyzed [3+3] Annulation Reaction of
Enynones/Enynals with Benzyl Azide
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Summary
In conclusion, we have discovered a new gold catalyzed regioselective [3+3] cycloaddition
reaction of enynones with benzyl azides that affords fused heterobicyclic furo[3,4-
d][1,2,3]triazines. Our methodology is further elaborated to enynals, providing [3+3]
cycloadducts. Interestingly though, enynones with an alkyl group (cf. Scheme 4) tend to undergo
[3+2] cycloaddition by using the -ene part and not the -yne part. We have also demonstrated the
ring opening of furo[3,4-d][1,2,3]triazines with CAN resulting in highly substituted 1,2,3-
triazines in excellent yields. Both furo[3,4-d][1,2,3]triazines and the derived 1,2,3-triazines show
good fluorescence activity.
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Experimental Section
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General Experimental Conditions: Chemicals and solvents were purified when required
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according to standard procedures.16 All reactions, unless stated otherwise, were performed in a
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dry nitrogen atmosphere. 1H, C and F NMR spectra were recorded in CDCl3 (unless stated
otherwise) with shifts referenced to SiMe4 (δ = 0) or CFCl3 (δ = 0). Infrared spectra were
recorded neat or by using KBr pellets. Melting points were determined by using a local hot-stage
melting point apparatus and are uncorrected (not calibrated). Elemental analyses were carried out
on a CHN analyzer. For TLC, glass microslides were coated with silica-gel-GF254 (mesh size
75 ) and spots were identified using iodine or UV chamber as appropriate. For column
chromatography, silica gel of 100-200 mesh size was used. LC-MS or HRMS (ESI-TOF)
equipment were used to record mass spectra for isolated compounds where appropriate. UV-
Visible absorption spectra and fluorescence spectra (THF solution) were recorded.
(i) Synthesis of functionalized enynones [1a-m], 6 and 7a-b enynals [4a-e]
Enynones [1a-m], enynals [4a-e], 6 and 7a-b were prepared based on the literature
reports oxidizing 3.5 mmol of the precursor alcohol by MnO2.17 Out of these, compounds 1c and
1d are new.
(E)-2-(3-fluorobenzylidene)-1,4-diphenylbut-3-yn-1-one (1c). Yellow solid. Yield 1.00 g
(84%); mp 60-62 oC; 1H NMR (400 MHz, CDCl3): 8.12-8.09 (m, 1H), 8.05 (d, J = 7.6 Hz, 2H),
7.52 (d, J = 7.6 Hz, 1H), 7.65-7.61 (m, 2H), 7.53 (t, J = 7.6 Hz, 2H), 7.48-7.41 (m, 3H), 7.38-
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7.35 (m, 3H), 7.19-7.15 (m, 1H); C NMR (100 MHz, CDCl3): 193.0, 162.7 (J = 244.4 Hz),
143.1 (J = 2.8 Hz), 137.0, 136.9, 136.8, 132.8, 131.4, 130.1, 130.0, 129.8, 129.1, 128.5, 128.2,
126.7 (J = 2.7 Hz), 122.3 (J = 42.2 Hz), 117.4 (J = 21.5 Hz), 116.1 (J = 22.7 Hz), 102.0, 86.8; IR
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(KBr): 3053, 2192, 1660, 1589, 1496, 1441, 1277, 1222, 1145, 986, 904, 778, 756, 718 cm–1;
LC/MS: m/z 327 [M+1]+. Anal. Calcd. for C23H15FO: C, 84.64; H, 4.63; Found: C, 84.52; H,
4.68.
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(E)-2-(4-fluorobenzylidene)-1,4-diphenylbut-3-yn-1-one (1d). Yellow solid. Yield 0.87 g
(88%); mp 62-64 oC; 1H NMR (400 MHz, CDCl3): 8.17 (dd, J = 8.8 Hz, 5.6 Hz, 2H), 8.04 (d, J
= 7.2 Hz, 2H), 7.64-7.60 (m, 2H), 7.52 (t, J = 7.6 Hz, 2H), 7.44-7.37 (m, 5H), 7.18 (t, J = 8.8 Hz,
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2H); C NMR (100 MHz, CDCl3): .193.2, 163.8 (J = 251.4 Hz), 143.7, 137.1, 132.6, 132.5,
132.4, 131.4, 131.2 (J = 3.3 Hz), 129.7, 129.0, 128.5, 128.1, 122.7, 120.5, 115.8 (J = 21.4 Hz),
101.0, 87.0; IR (KBr): 3052, 2186, 1666, 1605, 1573, 1512, 1452, 1310, 1233, 1156, 959, 827,
751, 690 cm–1; LC/MS: m/z 327 [M+1]+. Anal. Calcd. for C23H15FO: C, 84.64; H, 4.63; Found:
C, 84.75; H, 4.58.
(ii) Synthesis of azides [2a-k]
All these azides were synthesized following known literature procedures.18a Thus benzyl
and aliphatic bromides were subjected to SN2 displacement with NaN3 to afford azides (2a-i) and
2k. Azide 2j was prepared directly from alcohol using trimethylsilyl azide as the azide source.18b
(iii) Representative procedure for the preparation of compounds 3aa-ak and 3ba-ma
To an oven dried 5 mL RBF, LAu(CH3CN)SbF6 (L = [(2-biphenyl)di-tert-
butylphosphine]) (0.015 mmol) and benzyl azide 2a (0.36 mmol) in DCE (1 mL) were added, the
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mixture was kept at 0 C and the contents stirred for 5 min. (E)-2-Benzylidene-1,4-diphenylbut-
3-yn-1-one (1a, 0.30 mmol) in DCE was added dropwise to the above mixture. After completion
of the reaction, as monitored by TLC, the solvent was evaporated under vacuum. The residue
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was then purified by silica gel column chromatography by using hexane:EtOAc (49:1) as the
eluent to afford 3-benzyl-4,5,7-triphenyl-3,4-dihydrofuro[3,4-d][1,2,3]triazine 3aa. Compounds
3ab-ak and 3ba-ma were prepared following the same procedure and by using the same molar
quantities.
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3-benzyl-4,5,7-triphenyl-3,4-dihydrofuro[3,4-d][1,2,3]triazine (3aa). Yellow solid. Yield 0.111
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g (84%); mp 160-162 C; H NMR (400 MHz, CDCl3): 8.37 (d, J = 7.6 Hz, 2H), 7.52 (t, J =
7.6 Hz, 2H), 7.45-7.25 (m, 15H), 7.20 (t, J = 7.2 Hz, 1H), 5.58 (s, 1H), 5.25 (d, J = 15.2 Hz, 1H),
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4.39 (d, J = 15.2 Hz, 1H); C NMR (100 MHz, CDCl3): 145.1, 144.5, 139.9, 135.9, 129.70,
129.66, 129.02, 128.97, 128.8, 128.7, 128.5, 128.34, 128.28, 128.25, 128.1, 127.7, 125.6, 125.0,
107.0, 56.9, 55.9; IR (KBr): 3052, 3030, 2926, 2855, 1600, 1485, 1419, 1364, 1249, 1156, 1074,
942, 910, 762, 696 cm–1; HRMS (ESI): Calcd. for C30H24N3O [M++H]: m/z 442.1919. Found:
442.1918. X-ray structure has been determined for this compound.
3-(4-methoxybenzyl)-4,5,7-triphenyl-3,4-dihydrofuro[3,4-d][1,2,3]triazine (3ab). Yellow solid.
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Yield 0.110 g (78%); mp 154-156 C; H NMR (400 MHz, CDCl3): 8.37 (d, J = 8.0 Hz, 2H),
7.51 (t, J = 7.6 Hz, 2H), 7.43-7.25 (m, 12H), 7.22-7.18 (m, 1H), 6.96 (d, J = 8.0 Hz, 2H), 5.56 (s,
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1H), 5.19 (d, J = 14.8 Hz, 1H), 4.32 (d, J = 14.8 Hz, 1H), 3.85 (s, 3H); C NMR (100 MHz,
CDCl3): 159.5, 144.9, 144.3, 139.9, 129.7, 129.0, 128.7, 128.5, 128.4, 128.2, 127.7, 127.6,
125.6, 125.1, 125.0, 114.4, 107.0, 56.4, 55.6, 55.3; IR (KBr): 3063, 3024, 2827, 1610, 1512,
1484, 1435, 1243, 1166, 1123, 1079, 1029, 947, 766 cm–1; HRMS (ESI): Calcd. for C31H26N3O2
[M++H]: m/z 472.2025. Found: 472.2025.
3-(4-chlorobenzyl)-4,5,7-triphenyl-3,4-dihydrofuro[3,4-d][1,2,3]triazine (3ac). Yellow solid.
Yield 0.106 g (74%); mp 120-122 oC; 1H NMR (400 MHz, CDCl3): 8.37-8.35 (m, 2H), 7.51 (t,
J = 7.6 Hz, 2H), 7.40-7.26 (m, 14H), 7.23-7.19 (m, 1H), 5.52 (s, 1H), 5.17 (d, J = 15.2 Hz, 1H),
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4.37 (d, J = 15.2 Hz, 1H); C NMR (100 MHz, CDCl3): 145.3, 144.5, 139.6, 134.4, 133.9,
129.63, 129.59, 129.56, 129.2, 129.1, 128.9, 128.8, 128.5, 128.4, 128.3, 127.8, 125.6, 125.0,
124.9, 106.8, 56.2, 56.1; IR (KBr): 3063, 3025, 1589, 1496, 1458, 1436, 1260, 1129, 1074, 1008,
942, 762 cm–1; HRMS (ESI): Calcd. for C30H23ClN3O [M++H]: m/z 476.1529. Found: 476.1529.
3-(4-bromobenzyl)-4,5,7-triphenyl-3,4-dihydrofuro[3,4-d][1,2,3]triazine (3ad). Yellow solid.
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Yield 0.086 g (55%); mp 160-162 C; H NMR (400 MHz, CDCl3): 8.37-8.34 (m, 2H), 7.55-
7.49 (m, 4H), 7.40-7.32 (m, 6H), 7.30-7.25 (m, 6H), 7.21 (t, J = 7.2 Hz, 1H), 5.52 (s, 1H), 5.14
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(d, J = 15.2 Hz, 1H), 4.35 (d, J = 15.2 Hz, 1H); C NMR (100 MHz, CDCl3): 145.4, 144.6,
139.7, 135.0, 132.1, 129.9, 129.6, 129.1, 128.8, 128.7, 128.5, 128.3, 128.2, 127.8, 125.6, 125.1,
124.9, 122.0, 106.8, 56.3, 56.1; IR (KBr): 3063, 3025, 2921, 1671, 1600, 1485, 1447, 1403,
1266, 1123, 1068, 1008, 948, 767, 685 cm–1; HRMS (ESI): Calcd. for C30H23BrN3O [M++H] and
[M++H+2]: m/z 520.1024, 522.1024. Found: 520.1029, 522.1017.
3-(2-bromo-5-fluorobenzyl)-4,5,7-triphenyl-3,4-dihydrofuro[3,4-d][1,2,3]triazine (3ae). Yellow
solid. Yield 0.106 g (65%); mp 162-164 oC; 1H NMR (400 MHz, CDCl3): 8.37 (d, J = 8.0 Hz,
2H), 7.58-7.50 (m, 3H), 7.45 (d, J = 8.0 Hz, 2H), 7.41-7.30 (m, 8H), 7.26-7.22 (m, 1H), 7.18-
7.15 (m, 1H), 6.96-6.91 (m, 1H), 5.66 (s, 1H), 4.99 (d, J = 16.0 Hz, 1H), 4.74 (d, J = 16.0 Hz,
1H); 13C NMR (100 MHz, CDCl3): 162.3 (d, J = 246.4 Hz), 145.7, 144.5, 139.7, 138.1 (d, J =
6.9 Hz), 134.3 (d, J = 7.8 Hz), 129.6 (d, J = 2.6 Hz), 129.2, 129.0, 128.8, 128.7, 128.6, 128.2,
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127.9, 125.8, 125.0, 124.9, 117.6, 117.0, 116.8, 116.6, 107.0, 57.6, 56.6; F NMR (376 MHz,
CDCl3): -113.48; IR (KBr): 3058, 2921, 1660, 1585, 1490, 1463, 1441, 1266, 1129, 1074,
1030, 942, 773, 690 cm–1; LC/MS: m/z 538 [M]+ and 540 [M+2]+. Anal.Calcd. for
C30H21BrFN3O: C, 66.92; H, 3.93; N, 7.80; Found: C, 66.85; H, 3.87; N, 7.91.
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3-(4-nitrobenzyl)-4,5,7-triphenyl-3,4-dihydrofuro[3,4-d][1,2,3]triazine (3af). Yellow solid.
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Yield 0.077 g (53%); mp 138-140 C; H NMR (400 MHz, CDCl3): 8.36 (d, J = 8.4 Hz, 2H),
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7.55-7.50 (m, 4H), 7.40-7.32 (m, 6H), 7.30-7.25 (m, 6H), 7.21 (t, J = 7.2 Hz, 1H), 5.52 (s, 1H),
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5.14 (d, J = 15.2 Hz, 1H), 4.35 (d, J = 15.2 Hz, 1H); C NMR (100 MHz, CDCl3): 145.4,
144.6, 139.7, 135.0, 132.1, 129.9, 129.60, 129.59, 129.0, 128.8, 128.7, 128.5, 128.3, 128.2, 127.8,
125.6, 125.1, 124.9, 122.0, 106.8, 56.3, 56.2; IR (KBr): 3068, 2915, 1660, 1595, 1490, 1452,
1397, 1266, 1068, 1008, 942, 926 cm–1; HRMS (ESI): Calcd. for C30H23N4O3 [M++H]: m/z
487.1770. Found: 487.1775.
3-octyl-4,5,7-triphenyl-3,4-dihydrofuro[3,4-d][1,2,3]triazine (3ag). Yellow solid. Yield 0.120 g
(86%); mp 92-94 oC; 1H NMR (400 MHz, CDCl3): 8.35 (d, J = 8.0 Hz, 2H), 7.51-7.48 (m, 4H),
7.38-7.27 (m, 8H), 7.25-7.23 (m, 1H), 5.74 (s, 1H), 3.77-3.70 (m, 1H), 3.46-3.39 (m, 1H), 1.83-
1.67 (m, 2H), 1.33-1.28 (m, 10H), 0.89 (t, J = 6.8 Hz, 3H); 13C NMR (100 MHz, CDCl3):
144.7, 144.1, 140.5, 129.9, 129.8, 129.0, 128.7, 128.63, 128.59, 128.1, 128.0, 127.7, 125.5, 125.2,
125.0, 107.5, 57.4, 53.5, 31.8, 29.3, 29.2, 27.8, 26.7, 22.7, 14.1; (KBr): 3063, 2921, 2855, 1595,
1485, 1447, 1403, 1310, 1145, 1068, 1019, 948, 756, 690 cm–1; HRMS (ESI): Calcd. for
C31H34N3O [M++H]: m/z 464.2702. Found: 464.2706.
3-cinnamyl-4,5,7-triphenyl-3,4-dihydrofuro[3,4-d][1,2,3]triazine (3ah). Yellow solid. Yield
0.101 g (72%); mp 156-158 oC; 1H NMR (400 MHz, CDCl3): 8.36 (d, J = 8.2 Hz, 2H), 7.51 (t,
J = 8.0 Hz, 2H), 7.45 (t, J = 7.6 Hz, 4H), 7.39-7.31 (m, 11H), 7.22 (t, J = 7.2 Hz, 1H), 6.65 (d, J
= 16.0 Hz, 1H), 6.32-6.25 (m, 1H), 5.81 (s, 1H), 4.76-4.71 (m, 1H), 4.14-4.08 (m, 1H); 13C NMR
(100 MHz, CDCl3): 145.1, 144.4, 140.0, 136.3, 134.4, 129.7, 129.1, 128.73, 128.69, 128.6,
128.3, 128.1, 127.8, 126.6, 125.6, 125.1, 124.0, 107.2, 56.4, 55.7; IR (KBr): 3058, 3030, 2909,
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1605, 1496, 1447, 1260, 1123, 1074, 948, 767, 690 cm–1; HRMS (ESI): Calcd. for C32H26N3O
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[M++H]: m/z 468.2076. Found: 468.2073.
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(E)-3-(2-methyl-3-phenylallyl)-4,5,7-triphenyl-3,4-dihydrofuro[3,4-d][1,2,3]triazine
(3ai).
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Yellow solid. Yield 0.103 g (70%); mp 88-90 C; H NMR (400 MHz, CDCl3): 8.39-8.37 (m,
2H), 7.54-7.47 (m, 4H), 7.41-7.37 (m, 9H), 7.35-7.30 (m, 4H), 7.26-7.22 (m, 1H), 6.54 (s, 1H),
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5.75 (s, 1H), 4.68 (d, J = 14.8 Hz, 1H), 4.05 (d, J = 14.8 Hz, 1H), 1.98 (s, 3H); C NMR (100
MHz, CDCl3): 145.1, 144.5, 140.2, 137.1, 132.9, 129.8, 129.7, 129.1, 128.8, 128.7, 128.5,
128.39, 128.37, 128.3, 127.9, 127.0, 125.6, 125.13, 125.08, 107.2, 62.1, 55.9, 15.9; IR (KBr):
3058, 3031, 2921, 1606, 1496, 1425, 1326, 1260, 1129, 1085, 1008, 943, 773, 696 cm–1; LC/MS:
m/z 482 [M+1]+. Anal.Calcd. for C33H27N3O: C, 82.30; H, 5.65; N, 8.73; Found: C, 82.21; H,
5.63; N, 8.82.
4,5,7-triphenyl-3-(1-phenylethyl)-3,4-dihydrofuro[3,4-d][1,2,3]triazine (3aj). Yellow solid.
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Yield 0.104 g (76%); mp 180-182 C; H NMR (400 MHz, CDCl3): 8.38 (d, J = 8.0 Hz, 2H),
7.51 (t, J = 7.6 Hz, 2H), 7.44-7.43 (m, 4H), 7.39-7.32 (m, 9H), 7.23-7.24 (m, 2H), 7.19 (t, J = 7.6
Hz, 1H), 5.57 (s, 1H), 4.64 (qrt, J = 6.8 Hz, 1H), 1.73 (d, J = 6.8 Hz, 3H); 13C NMR (100 MHz,
CDCl3): 144.6, 144.5, 142.1, 140.7, 129.8, 129.7, 129.04, 128.95, 128.7, 128.4, 128.3, 128.1,
127.9, 127.6, 126.9, 125.5, 125.2, 125.1, 107.1, 61.7, 57.3, 22.6; IR (KBr): 3056, 3025, 2926,
1605, 1490, 1458, 1430, 1271, 1205, 1140, 1079, 1025, 937, 767, 685 cm–1; HRMS (ESI):
Calcd. for C31H26N3O [M++H] : m/z 456.2076. Found: 456.2076.
3-(anthracen-9-ylmethyl)-4,5,7-triphenyl-3,4-dihydrofuro[3,4-d][1,2,3]triazine (3ak). Yellow
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solid. Yield 0.132 g (80%); mp 220-222 C; H NMR (400 MHz, CDCl3): 8.52 (s, 1H), 8.31-
8.29 (m, 2H), 8.22-8.20 (m, 2H), 8.07-8.04 (m, 2H), 7.51-7.44 (m, 6H), 7.35-7.30 (m, 6H), 7.25-
7.20 (m, 4H), 7.18-7.14 (m, 1H), 6.03 (d, J = 14.8 Hz, 1H), 5.64 (d, J = 14.8 Hz, 1H), 5.50 (s,
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1H); 13C NMR (100 MHz, CDCl3): 145.2, 143.9, 140.8, 131.5, 131.4, 129.7, 129.6, 129.2,
129.0, 128.9, 128.7, 128.4, 128.2, 127.8, 127.7, 126.4, 125.8, 125.6, 125.1, 124.7, 124.4, 107.8,
56.6, 50.5; IR (KBr): 3068, 3035, 2938, 1605, 1592, 1486, 1448, 1427, 1272, 1150, 1075, 1017,
942, 766, 688 cm–1; HRMS (ESI): Calcd. for C38H28N3O [M++H] : m/z 542.2232. Found:
542.2225.
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3-benzyl-4-(4-methoxyphenyl)-5,7-diphenyl-3,4-dihydrofuro[3,4-d][1,2,3]triazine
(3ba).
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Yellow solid. Yield 0.099 g (70%); mp 110-112 C; H NMR (400 MHz, CDCl3): 8.38-8.36
(m, 2H), 7.51 (t, J = 8.0 Hz, 2H), 7.43-7.37 (m, 8H), 7.30-7.18 (m, 5H), 6.88 (d, J = 8.0 Hz, 2H),
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5.52 (s, 1H), 5.23 (d, J = 15.2 Hz, 1H), 4.41 (d, J = 15.2 Hz, 1H), 3.81 (s, 3H); C NMR (100
MHz, CDCl3): 159.8, 144.9, 144.3, 135.9, 132.1, 129.8, 129.7, 129.6, 129.0, 128.7, 128.5,
128.3, 128.2, 128.1, 127.6, 125.6, 125.2, 125.0, 114.3, 107.3, 56.8, 55.3; IR (KBr): 3047, 3019,
2953, 2921, 2833, 1611, 1512, 1496, 1447, 1425, 1255, 1173, 1101, 1068, 948, 822, 762, 685
cm–1; HRMS (ESI): Calcd. for C31H26N3O2 [M++H]: m/z 472.2025. Found: 472.2024.
3-benzyl-4-(4-fluorophenyl)-5,7-diphenyl-3,4-dihydrofuro[3,4-d][1,2,3]triazine (3ca). Yellow
solid. Yield 0.108 g (78%); mp 152-154 oC; 1H NMR (400 MHz, CDCl3): 8.36 (d, J = 7.6 Hz,
2H), 7.52 (t, J = 7.6 Hz, 2H), 7.46-7.35 (m, 8H), 7.30-7.25 (m, 4H), 7.23-7.19 (m, 1H), 7.05 (t, J
= 8.4 Hz, 2H), 5.58 (s, 1H), 5.25 (d, J = 15.2 Hz, 1H), 4.38 (d, J = 15.2 Hz, 1H); 13C NMR (100
MHz, CDCl3): 162.7 (J = 246.7 Hz), 145.3, 144.5, 135.73 (J = 3.1 Hz), 135.65, 130.1 (J = 8.4
Hz), 129.6 (J = 5.9 Hz), 129.0, 128.8, 128.5, 128.4, 128.21, 128.18, 127.9, 125.6, 125.0, 124.8,
116.0 (J = 21.7 Hz), 106.8, 56.9, 55.1; 19F NMR (376 MHz, CDCl3): -112.35; IR (KBr): 3047,
3030, 2926, 2866, 1605, 1490, 1447, 1227, 1156, 1085, 1079, 937, 833, 762, 690 cm–1; HRMS
(ESI): Calcd. for C30H23FN3O [M++H]: m/z 460.1825. Found: 460.1828.
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4-(4-fluorophenyl)-5,7-diphenyl-3-(1-phenylethyl)-3,4-dihydrofuro[3,4-d][1,2,3]triazine (3ch).
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Yellow solid. Yield 0.111 g (78%); mp 174-176 C; H NMR (400 MHz, CDCl3): 8.38-8.35
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(m, 2H), 7.50 (t, J = 8.0 Hz, 2H), 7.45-7.24 (m, 12H), 7.21-7.17 (m, 1H), 7.04 (t, J = 8.4 Hz,
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2H), 5.56 (s, 1H), 4.60 (qrt, J = 6.8 Hz, 1H), 1.73 (d, J = 6.8 Hz, 3H); C NMR (100 MHz,
CDCl3): 162.6 (J = 246.9 Hz), 144.6 (J = 26.9 Hz), 141.9, 136.5 (J = 3.4 Hz), 130.1, 130.0,
129.7, 129.5, 129.1, 128.7, 128.4, 128.2, 128.0, 127.8, 126.8, 125.5, 125.2, 124.9, 116.0 (J =
21.8 Hz), 106.9, 61.6, 56.4, 22.6; 19F NMR (376 MHz, CDCl3): -112.44; IR (KBr): 3058, 3026,
1606, 1507, 1430, 1233, 1151, 1074, 948, 816, 762, 690 cm–1; LC/MS: m/z 475 [M+1]+.
Anal.Calcd. for C31H24FN3O: C, 78.63; H, 5.11; N, 8.87; Found: C, 78.53; H, 5.06; N, 8.95.
3-benzyl-4-(3-fluorophenyl)-5,7-diphenyl-3,4-dihydrofuro[3,4-d][1,2,3]triazine (3da). Yellow
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solid. Yield 0.103 g (75%); mp 170-172 C; H NMR (400 MHz, CDCl3): 8.40-8.38 (m, 2H),
7.53 (t, J = 7.6 Hz, 2H), 7.47-7.28 (m, 11H), 7.25-7.21 (m, 1H), 7.11 (d, J = 8.0 Hz, 1H), 7.06-
13
7.01 (m, 2H), 5.60 (s, 1H), 5.29 (d, J = 15.0 Hz, 1H), 4.41 (d, J = 15.0 Hz, 1H); C NMR (100
MHz, CDCl3): 163.1 (J = 247.0 Hz), 145.5, 144.6, 142.2, 142.1, 135.6, 130.6 (J = 8.1 Hz),
129.5 (J = 5.6 Hz), 129.1, 128.8, 128.6, 128.4, 128.2, 127.9, 125.7, 125.0, 124.7, 124.0 (J = 2.7
Hz), 115.9 (J = 21.1 Hz), 115.3 (J = 21.7 Hz), 106.3, 57.0, 55.3; 19F NMR (376 MHz, CDCl3):
-111.36; IR (KBr): 3063, 2921, 1595, 1490, 1425, 1364, 1255, 1096, 1074, 942, 910, 762, 696
cm–1; HRMS (ESI): Calcd. for C30H23FN3O [M++H]: m/z 460.1825. Found: 460.1829.
3-benzyl-7-(4-methoxyphenyl)-4,5-diphenyl-3,4-dihydrofuro[3,4-d][1,2,3]triazine
(3ea).
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Yellow solid. Yield 0.091 g (64%); mp 150-152 C; H NMR (400 MHz, CDCl3): 8.32-8.30
(m, 2H), 7.45-7.24 (m, 14H), 7.19-7.15 (m, 1H), 7.06-7.04 (m, 2H), 5.55 (s, 1H), 5.23 (d, J =
13
14.8 Hz, 1H), 4.37 (d, J = 14.8 Hz, 1H), 3.92 (s, 3H); C NMR (100 MHz, CDCl3): 159.8,
145.5, 143.7, 139.9, 136.0, 129.8, 129.0, 128.9, 128.7, 128.5, 128.32, 128.27, 128.0, 127.5, 127.2,
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124.8, 123.9, 122.7, 114.3, 107.0, 56.8, 55.9, 55.4; IR (KBr): 3063, 3030, 2932, 2849, 1600,
1490, 1436, 1222, 1074, 942, 827, 762, 690 cm–1; HRMS (ESI): Calcd. for C31H26N3O2 [M++H]:
m/z 472.2025. Found: 472.2026.
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3-benzyl-4,5-diphenyl-7-(p-tolyl)-3,4-dihydrofuro[3,4-d][1,2,3]triazine (3fa). Yellow solid.
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Yield 0.090 g (66%); mp 198-200 C; H NMR (400 MHz, CDCl3): 8.28 (d, J = 8.0 Hz, 2H),
7.46-7.31 (m, 14H), 7.27 (t, J = 7.2 Hz, 2H), 7.19 (t, J = 7.2 Hz, 1H), 5.58 (s, 1H), 5.25 (d, J =
13
14.8 Hz, 1H), 4.40 (d, J = 14.8 Hz, 1H), 2.46 (s, 3H); C NMR (100 MHz, CDCl3): 145.5,
144.1, 139.9, 138.4, 136.0, 129.8, 129.5, 129.01, 128.97, 128.7, 128.5, 128.4, 128.3, 128.1, 127.6,
127.0, 125.6, 125.0, 124.6, 107.0, 56.9, 55.9, 21.6; IR (KBr): 3063, 3030, 2915, 2860, 1595,
1512, 1447, 1403, 1255, 1068, 959, 811, 696 cm–1; HRMS (ESI): Calcd. for C31H26N3O [M++H]:
m/z 456.2076,. Found: 456.2075.
3-benzyl-4,7-diphenyl-5-(o-tolyl)-3,4-dihydrofuro[3,4-d][1,2,3]triazine (3ga). Yellow solid.
o
1
Yield 0.102 g (75%); mp 96-98 C; H NMR (400 MHz, CDCl3): 8.39 (d, J = 7.6 Hz, 1H),
7.47-7.33 (m, 15H), 7.28 (t, J = 7.6 Hz, 2H), 7.22-7.18 (m, 1H), 5.62 (s, 1H), 5.27 (d, J = 15.2
13
Hz, 1H), 4.40 (d, J = 15.2 Hz, 1H), 2.76 (s, 3H); C NMR (100 MHz, CDCl3): 147.1, 144.7,
140.0, 136.2, 135.9, 131.5, 130.1, 129.8, 129.1, 129.0, 128.8, 128.7, 128.6, 128.4, 128.3, 128.1,
127.6, 126.1, 125.3, 124.8, 106.5, 56.9, 55.9, 22.1; IR (KBr): 3063, 3025, 2920, 1600, 1496,
1425, 1348, 1310, 1266, 1101, 1058, 931, 762, 707 cm–1; HRMS (ESI): Calcd. for C31H26N3O
[M++H]: m/z 456.2076. Found: 456.2077.
3-benzyl-7-(4-fluorophenyl)-4,5-diphenyl-3,4-dihydrofuro[3,4-d][1,2,3]triazine (3ha). Yellow
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solid. Yield 0.110 g (80%); mp 170-172 C; H NMR (400 MHz, CDCl3): 8.37-8.33 (m, 2H),
7.45-7.29 (m, 13H), 7.25-7.19 (m, 4H), 5.56 (s, 1H), 5.24 (d, J = 15.2 Hz, 1H), 4.39 (d, J = 15.2
Hz, 1H); 13C NMR (100 MHz, CDCl3): 162.7 (J = 247.6 Hz), 144.5, 144.3, 139.8, 135.8,
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131.5, 129.6, 129.1, 129.0, 128.9, 128.8, 128.5, 128.4, 128.3 (J = 3.1 Hz), 128.1, 127.8, 127.5,
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127.4, 126.1 (J = 3.0 Hz), 125.0, 124.6, 115.9 (J = 21.8 Hz), 106.9, 56.9, 55.9; F NMR (376
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MHz, CDCl3): -112.21; IR (KBr): 3068, 3030, 1600, 1501, 1452, 1348, 1227, 1151, 1090,
1068, 948, 833, 696 cm–1; HRMS (ESI): Calcd. for C30H23FN3O [M++H]: m/z 460.1825. Found:
460.1827.
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3-benzyl-7-(4-chlorophenyl)-4,5-diphenyl-3,4-dihydrofuro[3,4-d][1,2,3]triazine (3ia). Yellow
solid. Yield 0.110 g (80%); mp 170-172 oC; 1H NMR (400 MHz, CDCl3): 8.31 (d, J = 8.4 Hz,
2H), 7.48 (d, J = 8.4 Hz, 2H), 7.46-7.25 (m, 14H), 7.21 (t, J = 7.2 Hz, 1H), 5.25 (s, 1H), 5.24 (d,
J = 15.2 Hz, 1H), 4.40 (d, J = 15.2 Hz, 1H); 13C NMR (100 MHz, CDCl3): 144.9, 143.9, 139.8,
135.7, 133.9, 129.5, 129.05, 128.98, 128.97, 128.8, 128.5, 128.30, 128.28, 128.2, 128.1, 127.9,
126.7, 125.2, 125.1, 107.0, 57.0, 56.0; IR (KBr): 3058, 3025, 2910, 1595, 1480, 1436, 1414,
1353, 1249, 1090, 1063, 948, 833, 762, 696 cm–1; LC/MS: m/z 476 [M+1]+. Anal. Calcd. for
C30H22ClN3O: C, 75.70; H, 4.66; N, 8.83; Found: C, 75.58; H, 4.71; N, 8.76.
3-benzyl-7-(cyclohex-1-en-1-yl)-4,5-diphenyl-3,4-dihydrofuro[3,4-d][1,2,3]triazine
(3ja).
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Yellow solid. Yield 0.075 g (56%); mp 178-180 C; H NMR (400 MHz, CDCl3): 7.43-7.29
(m, 11H), 7.25-7.20 (m, 3H), 7.14 (t, J = 7.0 Hz, 1H), 6.97 (br, 1H), 5.49 (s, 1H), 5.19 (d, J =
15.2 Hz, 1H), 4.33 (d, J = 15.2 Hz, 1H), 2.80 (br, 2H), 2.38 (br, 2H), 1.87-1.85 (m, 2H), 1.77-
13
1.75 (m, 2H); C NMR (100 MHz, CDCl3): 147.4, 143.0, 140.0, 136.1, 129.9, 129.01, 128.9,
128.8, 128.6, 128.4, 128.3, 128.2, 128.0, 127.9, 127.3, 124.8, 124.1, 106.7, 56.7, 55.8, 25.9, 25.1,
22.4, 22.1; IR (KBr): 3057, 3024, 2920, 2854, 1649, 1599, 1495, 1446, 1177, 1068, 734, 690 cm–
1; HRMS (ESI): Calcd. for C30H28N3O [M++H]: m/z 446.2232. Found: 446.2236.
3-benzyl-5-(4-methoxyphenyl)-4,7-diphenyl-3,4-dihydrofuro[3,4-d][1,2,3]triazine
(3ka).
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Yellow solid. Yield 0.113 g (80%); mp 80-82 C; H NMR (400 MHz, CDCl3): 8.32-8.30 (m,
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2H), 7.50-7.40 (m, 8H), 7.36-7.34 (m, 1H), 7.26-7.18 (m, 4H), 7.04-7.01 (m, 2H), 6.93 (t, J = 7.6
Hz, 1H), 6.82 (d, J = 8.4 Hz, 1H), 5.70 (s, 1H), 5.35 (d, J = 14.8 Hz, 1H), 4.37 (d, J = 14.8 Hz,
1H), 3.49 (s, 3H); 13C NMR (100 MHz, CDCl3): 155.3, 145.2, 142.3, 140.9, 136.2, 130.0,
129.7, 129.1, 128.8, 128.7, 128.6, 128.0, 127.9, 127.0, 125.4, 124.9, 120.8, 119.3, 110.8, 109.4,
57.4, 55.4, 54.7; IR (KBr): 3052, 3030, 2921, 2833, 1600, 1584, 1485, 1458, 1430, 1315, 1249,
1107, 1019, 948, 756, 690 cm–1; HRMS (ESI): Calcd. for C31H26N3O2 [M++H]: m/z 472.2025.
Found: 472.2024.
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3-benzyl-4,7-diphenyl-5-(p-tolyl)-3,4-dihydrofuro[3,4-d][1,2,3]triazine (3la). Yellow solid.
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Yield 0.093 g (68%); mp 182-184 C; H NMR (400 MHz, CDCl3): 8.38 (d, J = 8.0 Hz, 2H),
7.52 (t, J = 7.2 Hz, 2H), 7.44-7.27 (m, 13H), 7.08 (d, J = 8.0 Hz, 2H), 5.57 (s, 1H), 5.25 (d, J =
13
14.8 Hz, 1H), 4.40 (d, J = 14.8 Hz, 1H), 2.31 (s, 3H); C NMR (100 MHz, CDCl3): 144.8,
140.0, 137.8, 135.9, 129.8, 129.2, 129.01, 128.97, 128.7, 128.4, 128.3, 128.12, 128.09, 126.9,
125.5, 125.1, 125.0, 106.3, 56.9, 55.9, 21.3; IR (KBr): 3068, 3030, 2910, 1605, 1512, 1485,
1452, 1430, 1266, 1112, 1068, 948, 816, 696 cm–1; HRMS (ESI): Calcd. for C31H26N3O [M++H]:
m/z 456.2076. Found: 456.2075.
3-benzyl-4,5-diphenyl-7-(o-tolyl)-3,4-dihydrofuro[3,4-d][1,2,3]triazine (3ma). Yellow solid.
Yield 0.103 g (76%); mp 62-64 oC; 1H NMR (400 MHz, CDCl3): 8.30-8.28 (m, 2H), 7.48 (t, J
= 7.6 Hz, 2H), 7.42-7.34 (m, 6H), 7.29-7.26 (m, 3H), 7.19 (t, J = 7.6 Hz, 1H), 7.14 (d, J = 7.2
Hz, 1H), 7.09-7.06 (m, 2H), 7.00 (t, J = 7.2 Hz, 1H), 6.75 (d, J = 7.6 Hz, 1H), 5.38 (s, 1H), 5.26
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(d, J = 15.2 Hz, 1H), 4.32 (d, J = 15.2 Hz, 1H), 2.19 (s, 3H); C NMR (100 MHz, CDCl3):
146.2, 145.3, 140.6, 137.7, 135.9, 130.5, 129.9, 129.5, 129.0, 128.9, 128.8, 128.7, 128.5, 128.4,
128.07, 128.05, 127.6, 125.34, 125.25, 123.8, 108.3, 57.1, 55.6, 20.4; IR (KBr): 3057, 3030, 2926,
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Calcd. for C31H26N3O [M++H]: m/z 456.2076. Found: 456.2074.
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(iv) Representative procedure for the synthesis of furo[3,4-d][1,2,3]triazine derivatives (5aa-
ea)
Compounds (5aa-ea) were prepared following the same procedure and the same molar
quantities as described for compounds 3aa-ma. But after the addition of all components, the
reaction was continued at 70 oC for 10h.
3-benzyl-4,7-diphenyl-3,4-dihydrofuro[3,4-d][1,2,3]triazine (5aa). Yellow solid. Yield 0.080 g
o
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(73%); mp 130-132 C; H NMR (400 MHz, CDCl3): 7.66-7.64 (m, 2H), 7.46-7.26 (m, 13H),
13
6.21 (s, 1H), 5.76 (s, 1H), 5.20 (d, J = 14.8 Hz, 1H), 4.25 (d, J = 14.8 Hz, 1H); C NMR (100
MHz, CDCl3): 152.3, 149.2, 140.9, 134.8, 129.7, 129.1, 129.0, 128.9, 128.8, 128.6, 128.3,
128.2, 127.6, 124.0, 104.4, 103.3, 60.5, 57.2; IR (KBr): 3053, 3030, 1540, 1485, 1479, 1458,
1392, 1353, 1315, 1255, 1101, 1063, 899, 762 cm–1; HRMS (ESI): Calcd. for C24H20N3O
[M++H]: m/z 366.1606. Found: 366.1605.
3-(4-methoxybenzyl)-4,7-diphenyl-3,4-dihydrofuro[3,4-d][1,2,3]triazine (5ab). Gummy liquid.
1
Yield 0.089 g (75%); H NMR (500 MHz, CDCl3): 7.65-7.63 (m, 2H), 7.45-7.34 (m, 6H),
7.30-7.29 (m, 1H), 7.28-7.27 (m, 1H), 7.23 (d, J = 9.0 Hz, 2H), 6.93 (d, J = 9.0 Hz, 2H), 6.20 (s,
13
1H), 5.74 (s, 1H), 5.13 (d, J = 14.5 Hz, 1H), 4.18 (d, J = 14.5 Hz, 1H), 3.85 (s, 3H); C NMR
(125 MHz, CDCl3): 159.6, 152.2, 149.2, 141.0, 130.0, 129.7, 129.1, 128.9, 128.7, 128.2, 127.6,
126.5, 124.0, 114.3, 104.3, 103.3, 60.3, 56.7, 55.3; IR (neat): 2920, 2860, 1610, 1517, 1484,
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1451, 1397, 1309, 1254, 1183, 1095, 1024, 766. cm–1; HRMS (ESI): Calcd. for C25H22N3O2
[M++H]: m/z 396.1712. Found: 396.1710.
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3-benzyl-7-(4-methoxyphenyl)-4-phenyl-3,4-dihydrofuro[3,4-d][1,2,3]triazine (5ba). Yellow
solid. Yield 0.081 g (68%); mp 148-150 oC; 1H NMR (400 MHz, CDCl3): 7.58 (d, J = 8.8 Hz,
2H), 7.45-7.37 (m, 5H), 7.33-7.28 (m, 5H), 6.90 (d, J = 8.8 Hz, 2H), 6.08 (s, 1H), 5.74 (s, 1H),
5.18 (d, J = 14.8 Hz, 1H), 4.23 (d, J = 14.8 Hz, 1H), 3.84 (s, 3H); 13C NMR (100 MHz, CDCl3):
159.7, 152.5, 148.8, 141.0, 134.9, 129.1, 128.93, 128.87, 128.6, 128.2, 127.6, 125.6, 122.7,
114.2, 104.5, 101.7, 60.5, 57.1, 55.3; IR (KBr): 2964, 2932, 2838, 1611, 1496, 1458, 1397, 1255,
1173, 1101, 1068, 937, 701 cm–1; HRMS (ESI): Calcd. for C25H22N3O2 [M++H]: m/z 396.1712.
Found: 396.1720.
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3-benzyl-7-(4-chlorophenyl)-4-phenyl-3,4-dihydrofuro[3,4-d][1,2,3]triazine (5ca). Yellow
solid. Yield 0.079 g (66%); mp 140-142 oC; 1H NMR (400 MHz, CDCl3): 7.56 (d, J = 8.4 Hz,
2H), 7.46-7.27 (m, 12H), 6.20 (s, 1H), 5.75 (s, 1H), 5.20 (d, J = 14.8 Hz, 1H), 4.25 (d, J = 14.8
Hz, 1H); 13C NMR (100 MHz, CDCl3): 151.1, 149.3, 140.8, 134.7, 133.9, 129.14, 129.06,
129.0, 128.9, 128.6, 128.3, 128.2, 127.6, 125.2, 104.4, 103.7, 60.5, 57.3; IR (KBr): 3063, 3030,
2932, 1622, 1540, 1490, 1468, 1452, 1386, 1315, 1238, 1101, 1068, 1008, 932, 893, 701 cm–1;
HRMS (ESI): Calcd. for C24H19ClN3O [M++H]: m/z 400.1216. Found: 400.1217.
3-benzyl-4-phenyl-7-(o-tolyl)-3,4-dihydrofuro[3,4-d][1,2,3]triazine (5da). Gummy liquid. Yield
0.082 g (70%); 1H NMR (400 MHz, CDCl3): 7.75-7.73 (m, 1H), 7.45-7.40 (m, 6H), 7.35-7.29
(m, 5H), 7.23-7.21 (m, 2H), 6.11 (s, 1H), 5.79 (s, 1H), 5.20 (d, J = 15.2 Hz, 1H), 4.26 (d, J =
13
15.2 Hz, 1H), 2.45 (s, 3H); C NMR (100 MHz, CDCl3): 152.0, 148.8, 140.9, 134.9, 134.8,
131.3, 129.1, 129.0, 128.9, 128.7, 128.3, 128.2, 127.7, 127.1, 126.1, 106.8, 104.0, 60.5, 57.2,
22.1; IR (neat): 3068, 3025, 2926, 2099, 1688, 1600, 1490, 1457, 1392, 1310, 1101, 1074, 1025,
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380.1767.
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liquid. Yield 0.085 g (72%); H NMR (400 MHz, CDCl3): 7.44-7.38 (m, 8H), 7.35-7.31 (m,
4H), 7.29-7.27 (m, 1H), 7.00-6.95 (m, 1H), 6.23 (s, 1H), 5.75 (s, 1H), 5.20 (d, J = 15.2 Hz, 1H),
4.25 (d, J = 15.2 Hz, 1H); 13C NMR (125 MHz, CDCl3): 163.1 (d, J = 244.4 Hz), 150.9 (d, J =
3.4 Hz), 149.4, 140.8, 134.7, 131.7 (d, J = 8.4 Hz), 130.8, 130.4 (d, J = 8.8 Hz), 129.2, 129.1,
128.9, 128.6, 128.3, 127.6, 119.6 (d, J = 2.9 Hz), 115.0 (d, J = 21.0 Hz), 110.9 (d, J = 23.6 Hz),
19
104.3, 60.5, 57.3; F NMR (470 MHz, CDCl3): -112.48; IR (neat): 3068, 3030, 2920, 1625,
1605, 1589, 1485, 1457, 1397, 1342, 1266, 1194, 1096, 1025, 948, 778, 696 cm–1; HRMS (ESI):
Calcd. for C24H19FN3O [M++H]: m/z 384.1512. Found: 384.1510.
(v) Synthesis of highly functionalized triazine derivatives 8 and 9aa-9ba
Compounds 8 and 9aa-9ba were prepared following the same procedure and the same molar
quantities as described for compounds 3aa-3ak.
1-(1-benzyl-5-phenyl-4-(phenylethynyl)-4,5-dihydro-1H-1,2,3-triazol-4-yl)ethanone
(8)
1
Gummy liquid. Yield 0.074 g (75%); H NMR (400 MHz, CDCl3): 7.53-7.51 (m, 2H), 7.44-
7.31 (m, 8H), 4.17 (d, J = 14.0 Hz, 1H), 3.81 (d, J = 14.0 Hz, 1H), 2.69-2.63 (m, 2H), 2.20-2.01
13
(m, 3H), 1.98-1.93 (m, 1H), 1.72-1.66 (m, 1H); C NMR (100 MHz, CDCl3): 202.8, 138.7,
132.1, 128.6, 128.5, 128.3, 127.9, 127.2, 122.4, 86.9, 82.7, 58.6, 52.8, 44.2, 36.8, 23.4, 19.2; IR
(Neat): 3063, 2937, 2855, 1704, 1644, 1485, 1452, 1359, 1216, 1096, 1030, 756, 690 cm–1;
HRMS (ESI): Calcd. for C21H20N3O [M++H]: m/z 330.1606. Found: 330.1607.
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The Journal of Organic Chemistry
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1-(1-benzyl-5-phenyl-4-(phenylethynyl)-4,5-dihydro-1H-1,2,3-triazol-4-yl)ethanone
(9aa)
5
6
7
8
1
Gummy liquid. Yield 0.068 g (60%); H NMR (400 MHz, CDCl3): 7.41-7.39 (m, 3H), 7.35-
7.27 (m, 6H), 7.24-7.20 (m, 2H),7.15-7.13 (m, 2H), 7.05-7.03 (m, 2H), 5.28 (d, J = 14.8 Hz, 1H),
5.06 (s, 1H), 4.29 (d, J = 14.8 Hz, 1H), 2.69 (s, 3H); 13C NMR (100 MHz, CDCl3): 197.7,
134.6, 134.2, 131.5, 128.80, 128.77, 128.7, 128.5, 128.4, 128.1, 121.7, 93.2, 92.1, 81.9, 63.4,
52.1, 26.8; IR (Neat): 3058, 2926, 2849, 1715, 1666, 1627, 1556, 1501, 1458, 1397, 1266, 1167,
1068, 756, 701 cm–1; HRMS (ESI): Calcd. for C25H22N3O [M++H]: m/z 380.1763. Found:
380.1763.
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1-(1-benzyl-5-phenyl-4-(phenylethynyl)-4,5-dihydro-1H-1,2,3-triazol-4-yl)ethanone
(9ba)
1
Gummy liquid. Yield 0.077 g (65%); H NMR (400 MHz, CDCl3): 7.40-7.38 (m, 3H), 7.35-
7.33 (m, 3H), 7.30-7.26 (m, 6H), 7.23-7.19 (m, 4H), 7.14-7.11 (m, 2H), 7.00-6.98 (m, 2H), 5.27
(d, J = 15.2 Hz, 1H), 5.04 (s, 1H), 4.28 (d, J = 15.2 Hz, 1H), 3.58-3.40 (m, 2H), 3.00 (t, J = 7.6
Hz, 2H); 13C NMR (100 MHz, CDCl3): 199.3, 140.6, 134.6, 134.1, 131.5, 128.8, 128.7, 128.53,
128.46, 128.43, 128.35, 128.1, 121.6, 93.2, 91.8, 81.9, 63.7, 52.1, 40.8, 29.8; IR (Neat): 3030,
2920, 2214, 1730, 1605, 1506, 1462, 1364, 1271, 1150, 1073, 1024, 761, 706.cm–1; HRMS
(ESI): Calcd. for C32H28N3O [M++H]: m/z 470.2232. Found: 470.2229.
(vi) General procedure for the synthesis of tetrasubstituted 1,2,3-triazines (10-13)
A solution of cerium(IV) ammonium nitrate (CAN)19 (124.5 mg, 0.22 mmol) in water (2
mL) was added dropwise to a stirring solution of the 3aa (50.0 mg 0.11 mmol) in acetonitrile (3
mL). The mixture was stirred at rt for 15 min and then extracted with chloroform (3×20 mL).
The combined organic layer was washed with brine solution, dried over anh. sodium sulfate and
concentrated in vacuum. The residue was then purified by silica gel column chromatography
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