Studies towards iodine-catalyzed dehydrative-cycloisomerization of pent-4-yne-1,2-diols to di- and tri-substituted furans

Article abstract of DOI:10.1016/j.tet.2018.08.032

An efficient and single-step iodine catalyzed and metal-free synthesis of di and tri-substituted 2-methylfuran derivatives were achieved from 1-popargyl-1,2-diols. Stereospecific synthesis of starting 1,2-diols was achieved by indium mediated Barbier type

Full text of DOI:10.1016/j.tet.2018.08.032

Accepted Manuscript
Studies towards iodine-catalyzed dehydrative- cycloisomerization of pent-4-yne-1,2-
diols to di- and tri-substituted furans
H. Surya Prakash Rao, Vijjapu Satish, Silambarasan Kanniyappan, Priyanka Kumari
PII:
S0040-4020(18)30997-9
10.1016/j.tet.2018.08.032
TET 29752
DOI:
Reference:
To appear in: Tetrahedron
Received Date: 3 July 2018
Revised Date: 7 August 2018
Accepted Date: 21 August 2018
Please cite this article as: Rao HSP, Satish V, Kanniyappan S, Kumari P, Studies towards iodine-
catalyzed dehydrative- cycloisomerization of pent-4-yne-1,2-diols to di- and tri-substituted furans,
Tetrahedron (2018), doi: 10.1016/j.tet.2018.08.032.
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ACCEPTED MANUSCRIPT
Studies towards iodine-catalyzed dehydrative- cycloisomerization of pent-4-yne-1,2-diols to
di- and tri-substituted furans
H. Surya Prakash Raoa,b*, Satish Vijjapua, Silambarasan Kanniyappana, Priyanka Kumaria
a Department of Chemistry, Pondicherry University, Pondicherry – 605 014. India.
b Department of Chemistry and Biochemistry, School of Basic Science and Research, Sharda
University, Greater Noida – 201306. India
ABSTRACT
An efficient and single-step iodine catalyzed and metal-free synthesis of di and tri-
substituted 2-methylfuran derivatives were achieved from 1-popargyl-1,2-diols. Stereospecific
synthesis of starting 1,2-diols was achieved by indium mediated Barbier type propargylation on
corresponding keto-alcohols or by sodium borohydride mediated reduction of 2-hydroxy-2-
propargyl ketones. The furan synthesis proceeded through iodine mediated 5-exo-trig
cyclization, dehydration and reductive deiodination. The method was applied to the synthesis of
2-methylfuran fused to phenanthrene, pyrene and acenaphthylene rings.
Keywords:
1. Furan synthesis
2. Iodine
3. Propargylated 1,2-diol
4. Reductive deiodination
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1. Introduction
Furan is an oxygen containing five-membered hetero-aromatic compound of fundamental
importance.1 Its motif is present in a large number of natural products and medicinal drugs.2
Moreover, several furan derivatives serve as useful intermediates in synthetic chemistry.3 In view
of its importance, development of new methods for synthesis of various furan derivatives has
attracted considerable attention of chemists from the beginning of the field of Heterocyclic
Chemistry.4 Even after over one hundred twenty five years of the first synthesis of furan,5 there
is still room and indeed need for efficient and operationally simpler methods to hitherto unknown
furans.6 Acid catalyzed dehydrative transformation of acyclic 1,4-dicarbonyl compounds into the
furan derivatives is a classical method.7 In recent years, several new syntheses have been
reported, in which acyclic precursors with an acetylenic group were converted into furan
derivatives.8 We have been interested in the synthesis of furans fused to polycyclic aromatic
hydrocarbons (PAHs) to study their photochromic properties. Recently we have described a two-
step synthesis of 2-methylfuran fused to pyrene ring 2 from corresponding allyl substituted
vicinal diol 1 (Scheme 1).9 The iodine induced cyclization of 1 followed by dehydration lead to
intermediate dihydrofuran, which on base mediated elimination of HI furnished furan-pyrene
fused compound 2. In continuation of this work, we planned a two-step one-pot synthesis of
2,3,5-trisubstituted furans like 5 from 1,2-diols having propargyl substitution e.g. 3 by using
iodine as the reagent to induce coveted cyclization.10 We reasoned that in the first-step 3 could
undergo iodine mediated 5-exo-dig cyclization11 to form corresponding iodomethylfurans 4,
which on reductive deiodination could furnish 2,3-disubstituted 5-methyl furans 5 (Scheme 1).
However, when we conducted the reaction on 3a (Ar = Ph), serendipitously, discovered that 2,3-
diphenyl 5-methylfuran 5a (Ar = Ph) has formed in the reaction. The reaction apparently went
through in-situ unprecedented reductive deiodination of the intermediate 4a (Ar = Ph). Herein,
we describe the scope of this facile iodine catalyzed and metal-free transformation of pent-4-yne-
1,2-diols for a practical and scalable synthesis of 2-aryl-5-methylfurans, 3-aryl-5-methylfurans
and 2,3-diaryl-5-methylfurans. Iodine is an inexpensive, non-toxic and readily available weak
and soft Lewis acid useful for various organic transformations.12 Generally, iodine mediated
organic transformations provide excellent yield of the products with high regio, chemo and
stereo-selectivity.
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Scheme 1. Two-step transformation of vicinal diol 1 into furan fused pyrene 2 and proposed
scheme for the synthesis of 2,3-diaryl-5-methyl furans 5 from corresponding pent-4-yne-1,2-
diols 3.
2. Results and discussion
Hitherto unknown propargylic 1,2-diols 3 are the starting compounds for the present
work. They can be prepared either by propargylation of α-hydroxyketones 6 (eg. benzoins) or by
propargylation followed by reduction of 1,2-carbonyl compounds 7 (e.g. benzils). We have
explored both the methods. The Barbier type reaction of α-hydroxyketones 6a-e with propargyl
bromide in the presence of indium metal provided (1RS,2SR)-1,2diarylpent-4-yne-1,2-diols 3a-e
in good yield as single diastereomers (Scheme 2). The high diastereoselectivity (>99%) is in
agreement with the Cram’s chelation model13 and literature precedence of the indium mediated
Barbier type allylation on benzoin 5a.14
Scheme 2. Two-step synthesis of 2,3-disubstiutted 5-methylfurans from α-hydroxyketones.
In contrast to the propargylation of α-hydroxyketones 6, which provided stereoselective
propargylated products 3, the reaction on the 1,2-diketone 7 (benzil) under above reaction
conditions provided an inseparable mixture of α-hydroxy α-allenyl ketone 8 and α-hydroxy α-
propargyl ketone 9 in 3:2 ratio (Scheme 3). Reduction of the mixture with sodium borohydride
furnished diastereomeric mixture of syn-vicinal diols 10 and 3a along with anti-vicinal diols
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11and 12. Incisive analysis of the 1H and 13C NMR spectra indicated that syn-vicinal diol 3a was
the major product (70%) and anti-vicinal diol 12 (30%) was the minor product. The result is in
agreement with the outcome of the reduction predicted by applying Felkin-Anh model15 and by
considering that phenyl group is bulkier than the propargyl group.16
Scheme 3. Indium mediated Barbier type propargylation of benzyl 7 followed by reduction to
form vicinal diols 10-12 and 3a.
Next, we subjected the syn-1,2-diphenyl pent-4-yne-1,2-diol 3a to iodine mediated
cyclization to generate furan 5a and to work out optimal reaction conditions (Scheme 2). The
reaction of 3a with one equivalent of iodine in dry THF at rt surprisingly provided known17 2,3-
diphenyl-5-methylfuran 5a as the only product in 90% yield. There was no trace of iodine
incorporated product 4a (formed via 5-exo-dig cyclization, followed by dehydration and double
bond rearrangement) or 13a (formed via 5-endo-dig cyclization). Since the product 5a did not
have iodine, we hypothesized that the reductive removal of iodide from the intermediate 4a to
form 5a and regeneration of iodine was the final-step in the reaction sequence. Therefore, the
reaction could work with a catalytic amount of iodine. Indeed, the transformation took place with
10 mol% of iodine, although yield was lower (65%). Switch over from refluxing THF to
refluxing 1,4-dioxane resulted in an increase of the yield up to 90% (Scheme 2). With optimized
conditions in hand, we expanded the substrate scope of the reaction by converting four pent-4-
yne-1,2-diols 3b-e into hitherto unknown 2,3-diaryl-5-methylfurans 5b-e (Scheme 2). It is
noteworthy that the transformation worked well with bis-aromatic 3a-c, aromatic and aliphatic
3d propargylic 1,2-diols to provide corresponding furans 5a-d. However, when both R1 and R2
were alkyl groups, e.g. 3e, the product 5e (IR, NMR, ESI-MS) formation was observed, but
possibly due to its low stability column chromatographic purification was not possible. Of the
five products, 5c is interesting as the two naphthalene rings in it could align one above the other
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like in a cleft (see Figure 1; DFT/B3LYP/6-311G(d,p) energy minimized structure; using
Gaussian 09) and act as a host for suitable aromatic guest molecules.
Figure 1. The energy minimized structure of 5c.
After establishing a reliable procedure for the synthesis of 2,3-disubstituted-5-
methylfurans e.g. 5a we explored the possibilities of synthesis of 5-methylfuran fused to
phenanthrene 14, pyrene 2 and acenaphthylene 15 rings (Figure 2) to extend the scope of the
procedure and for the synthesis of furan fused polycyclic aromatic hydrocarbons (PAHs).
Figure 2. Structures of 5-methylfuran fused stilbene 5a, phenanthrene 14, pyrene 2 and
acenaphthylene 15.
Syntheses of 5-methylfuran fused PAHs 14, 2 and 15 were achieved through three-step
protocol from corresponding 1,2-diketones 16a-c as given in Scheme 4. The indium metal
mediated Barbier type reaction with propargyl bromide on one of the carbonyl groups in 16a-c
furnished keto alcohols 17a-c in excellent yield (Scheme 5).18 Interestingly there were no allenyl
products like 8 in the reaction mixture. The neighboring hydroxy group assisted the
stereoselective reduction of the carbonyl group in 17a-c with sodium borohydride furnished
trans-diols 18a-c. Stereochemistry of the vicinal hydroxyl group in 18a-c as trans was finalized
on the basis of spectral (IR, 1H NMR, 13C NMR, DEPT-135, 2D NMR HSQC, HMBC, COSY
and NOESY) data and X-ray crystal structure analysis of (9RS, 10RS)-9-allyl-9,10-
dihydrophenanthrene-9,10-diol.19 The iodine mediated cyclization of 18a-c delivered 5-
methylfuran fused phenanthrene 14, pyrene 2 and acenaphthylene 15 respectively in good yields.
Each of them displayed furyl methyl group as a doublet at δ 2.6 (J = 1.0 Hz) ppm.
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Scheme 4. Three-step synthesis of 5-methylfuran appended PAHs 14, 2 and 15 from
corresponding 1,2-diones 16a-c.
After demonstrating the iodine mediated synthesis of 2,3-diaryl-5-methylfurans, we
extended the study to the synthesis of C(4) substituted 2-methylfurans. Thus, propargylated 1,2-
diols 20a-d were subjected iodine mediated dehydrative cyclization to realize C(4) aryl 2-
methylfurans 21a-d 20 in good yield (Scheme 5). The propargylated 1,2-diols 20a-d were
prepared from 2-hydroxyethanones 19a-c by indium mediated propargylation.
Scheme 5. Two-step synthesis of C(4)aryl 2-methylfurans from corresponding 2-hydroxy-1-aryl
ethanones 19a-d.
After demonstrating the use of iodine in the synthesis of 3- and 2,3-substituted 5-
methylfurans we explored the scope of the transformation for the synthesis of 2-methyl-5-
phenylfuran 25 from corresponding propargylated 1,2-diols 23 and 24 (Scheme 6). Indium
mediated propargylation of phenyl glyoxal 22 provided 2-hydroxy-1-phenylpent-4-yn-1-one in
76% yield. Further reduction with sodium borohydride provided an inseparable mixture of
diastereomers 23 (C(1): RS; C(2): RS) and 24 (C(1): RS; C(2): SR) in 8:2 ratio in 92% yield. The
stereochemistry of diols was confirmed by comparing the NOESY spectral data of the parent
mixture and the corresponding acetonides 26 and 27. The acetonides were separated and
characterized independently.21 Reaction of the mixture of diols 23 and 24 with catalytic amount
of iodine provided known22 2-methyl-5-phenylfuran 25 in 88% yield.
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Scheme 6. Synthesis of 2-methyl-5-phenylfuran 25 from phenyl glyoxal 22.
Possible mechanism for the transformation of propargylated 1,2-diols e.g. 3a into 2-
methylfurans e.g. 5a is given in Scheme 7. The first-step is the electrophilic addition of iodine to
the triple bond in 3a to generate iodonium ion intermediate 28. Subsequent 5-exo-trig-
cyclization lead to vinyl iodide 29. Step-wise 1,3-prototopic shifts in 29 via 30 lead to the
intermediate 31. Dehydration to trisubstituted 2-iodomethylfuran 4a followed by reductive
deiodinationyielded stable 2,3-diphenyl-5-methylfuran 5a.To rule out the possibilities that iodine
assisted dehydration precedes cyclization, we exposed 3a to catalytic (10mol%) of p-
tolunesulfornicacid intoluene at 70 oC, conc. H2SO4 in dichloromethane at rt and F3B:OEt2 in
dichloromethane at rt. In all the cases furan did not form but there was extensive decomposition
of the 1,2-diol. To rule out radical intermediates, we conducted the reaction of 3a with catalytic
amount of iodine in dark in 1,4-dioxane reflux. The transformation was efficient to provide 5a in
90% yield. The reaction conducted at rt and in dark, as anticipated, took longer time (16 h) to
provide the product 5a but in lower yield (55%) and starting diol 3a was still remained (35%).
These results indicate that radical intermediates may not have formed enroute to furan 5a. To
further rule out involvement of radical intermediates we conducted the reaction in presence of
one equivalent of Edaravone (3-methyl-1-phenyl-2-pyrazolin-5-one) a radical quencher.23 Even
in this reaction, product 5a formed efficiently (71%). Based on above experiments, we conclude
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that the cyclization involving iodinium ion and reductive deiodination were the crucial steps in
the formation of the furan ring.
Scheme 7. Proposed mechanism for the iodine catalyzed dehydrative cyclization of 4-yne-1,2-
diols, e.g. 3a to furnish 2,3-diaryl-5-methyl furans e.g. 5a.
3. Conclusion
In summary, we have developed a new single-step iodine mediated metal-free synthesis
of 2-aryl, 3-aryl, and 2,3-diaryl 5-methylfurans from propargylated 1,2-diols. Key finding of this
study is the reductive deiodination of the plausible 5-iodomethylfuran intermediate. Starting
propargylated 1,2-diols were prepared by indium mediated Barbier type alkylation of
corresponding α-hydroxyketones. To best of our knowledge, reductive deiodination for the
conversion of 3 to 5 is unprecedented.
Experimental section
4.1 General Remarks
All reactions and chromatographic separations were monitored by thin layer
chromatography (TLC). Glass plates coated with silica gel GF-254 was used for TLC. Column
chromatography was carried on silica gel (100-200 mesh, AVRA synthesis private limited) using
increasing percentage of ethyl acetate in hexanes. Melting points were uncorrected and were
determined using open-ended capillary tubes on VEEGO VMP-DS instrument. IR spectra were
recorded as KBr pellets on a Nicolet-6700 spectrometer. 1H NMR spectra (400 MHz), 13C NMR
(100MHz) and DEPT-135 spectra were recorded for (CDCl3 or CDCl3 + CCl4, 1:1) solutions on
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Bruker-Avance 400 MHz spectrometer with TMS as internal standard. 1H-NMR data are
reported as follows: chemical shift (multiplicity (s = singlet, d = doublet, t = triplet, m =
multiplet, dd = doublet of the doublet, dt = doublet of the triplet, td = triplet of the doublet and
brs = broad singlet), coupling constant (J) and integrations. Coupling constant J values are given
in Hz. The 13C NMR spectra were recorded with broadband 1H decoupling. The DEPT-135
NMR spectra were recorded for each sample to support assigned structure. High resolution mass
spectra were recorded on a Water Q-TOF micro mass spectrometer using electron spray
ionization mode. The X- ray diffraction measurements were carried out at 298 K on Oxford
CrysAlis CCDCarea detector system equipped with a graphite monochromator and a Mo-Kα
fine-focus sealed tube (λ = 0.71073 Å).
4.2 General procedure for reduction of α-hydroxy ketones: To the solution of α-hydroxy
ketones (1 mmol) dissolved in dry methanol (MeOH; 3 mL) and cooled to 0 oC sodium
borohydride (74 mg, 2 equiv) was added under nitrogen atm at 0 oC and stirred for 10 min and
then allowed to stir at for 2 h. After the completion of the reaction (TLC) MeOH was evaporated
under reduced pressure and then diluted with DCM (30 mL). The DCM layer was washed with
water (2 × 30 mL), brine (2 × 30 mL) and dried over anhydrous sodium sulfate. Removal of
DCM under reduced pressure resulted in crude product which was purified by column
chromatography using silica gel (100-200 mesh) and increasing amounts of (5 to 10%) EtOAc in
hexanes to afford 1,2-diols.
4.2a. 10-Hydroxy-10-(prop-2-yn-1-yl)phenanthren-9(10H)-one (17a):
O
OH
White solid;yield 82%; mp. 131-132 ºC (Reported mp. 130-133 ºC); IR (KBr) νmax 3467, 3261,
3069, 1691, 1599, 1447, 1415, 1374, 1316, 1290, 1241, 1217, 1136, 1100, 1031, 987, 937, 783,
754, 729, 690 cm-1; 1H NMR (400 MHz, CDCl3 + CCl4) δ 7.87 (d, J = 7.4 Hz, 1H), 7.81 (d, J=
8.0 Hz, 1H), 7.75-7.67 (m, 2H), 7.58 (s, 1H), 7.36-7.27 (m, 3H), 4.25 (s, 1H), 2.63-2.47 (m, 2H),
1.92 (t, J = 2.4 Hz, 1H) ppm; 13C NMR (100 MHz, CDCl3 + CCl4) δ 200.9 (C=O), 139.2 (C),
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137.6 (C), 135.2 (CH), 129.5 (CH), 129.3 (C), 128.8 (CH), 128.7 (CH), 128.3 (C), 127.8 (CH),
126.5 (CH), 124.2 (CH), 123.3 (CH), 78.0 (acetylinic C), 73.0 (acetylinic C), 35.6 (CH2).ppm;
HRMS (ESI) calcd for C17H13O2 [M + H]+ 249.0910, found 249.0928.
4.2b. 5-Hydroxy-5-(prop-2-ynyl)pyren-4(5H)-one (17b):
O
OH
Light yellow solid; yield 68%; mp. 115-116 ºC; IR (KBr) νmax 3478, 3295, 3054, 2923, 1690,
1620, 1587, 1423, 1337, 1294, 1227, 1171, 1146, 1035, 838, 721, 659 cm-1; 1H NMR (400 MHz,
CDCl3 + CCl4) δ 8.32 (dd, J = 7.4, 1.2 Hz, 1H), 8.17 (dd, J = 8.0, 1.2 Hz, 1H), 8.02 (dd, J = 7.4,
1.2 Hz, 1H), 7.89-7.69 (m, 5H), 4.52 (s, 1H), 2.78-2.63 (q, 2H), 2.04 (t, J = 2.7 Hz, 1H) ppm; 13C
NMR (100 MHz, CDCl3 + CCl4) δ 201.1 (C=O), 139.0 (C), 134.7 (CH), 132.0 (C), 131.2 (C),
129.8 (C), 128.1 (CH), 127.9 (CH), 127.8 (CH), 127.2 (CH), 127.0 (C), 126.6 (CH), 126.4 (CH),
124.4 (CH), 123.6 (C), 78.8 (C), 77.9 (acetylinic C), 73.1 (acetylinic C), 35.9 (CH2) ppm; HRMS
(ESI) calcd for C19H12O2Na [M + Na]+ 295.0735, found 295.0738.
4.2c. 2-Hydroxy-2-(prop-2-yn-1-yl)acenaphthylen-1(2H)-one (17c):
HO
O
Light yellow semi solid; yield 82%; mp. 128-130 ºC; IR (KBr) νmax 3423, 3297, 3060, 2926,
2118, 1953, 1773, 1725, 1604, 1493, 1465, 1428, 1343, 1305, 1262, 1217, 1183, 1137, 1183,
1072, 1016, 954, 837, 868, 782, 705, 657 cm-1; 1H NMR (400 MHz, CDCl3) δ 8.14 (d, J = 8.1
Hz, 1H), 7.97 (d, J = 7.0 Hz, 1H), 7.92 (d, J = 8.4 Hz, 1H), 7.85 (d, J = 8.0 Hz, 1H), 7.76-7.67
(m, 2H), 3.32 (s, 1H), 2.99 (dd, J = 16.6, 2.6 Hz, 1H), 2.78 (dd, J = 16.6, 2.6 Hz, 1H), 1.95 (t, J =
2.5 Hz, 1H); 13C NMR (100 MHz, CDCl3) δ 203.6 (C=O), 141.7 (C), 138.5 (C), 132.4 (CH),
130.7 (C), 130.4 (C), 128.9 (CH), 128.5 (CH), 126.0 (C), 122.6 (CH), 121.0 (CH), 78.3
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(acetylinic C), 71.9 (acetylinic C), 28.5 (CH2) ppm; HRMS (ESI) calcd for C15H10O2Na [M +
Na]+245.0573, found 245.0595.
4.2d. 2-Hydroxy-1-phenylpent-4-yn-1-one (20):
O
OH
Light yellow semi solid; yield 76%; IR (KBr) νmax 3404, 3354, 2974, 2951, 1697, 1597, 1450,
1222, 1111, 961, 844, 715, 684 cm-1; 1H NMR (400 MHz, CDCl3 + CCl4) δ 7.91 (dd, J = 8.3, 1.0
Hz, 2H), 7.59 (t, J = 7.3 Hz, 1H), 7.48 (t, J = 7.8 Hz, 2H), 5.20 (t, J = 5.1 Hz, 1H), 2.82-2.76 (m,
1H), 2.61-2.54 (m, 1H), 2.00 (t, J = 2.6 Hz, 1H) ppm; 13C NMR (100 MHz, CDCl3) δ 199.3
(C=O), 134.1 (CH), 133.6 (C), 128.9 (CH), 128.7 (CH), 78.6 (C), 72.1 (CH), 71.0 (CH), 26.1
(CH2) ppm; HRMS (ESI) calcd for C11H10O2Na [M + Na]+ 197.0573, found 197.0578.
4. 3 General procedure for indium metal mediated Barbier type reaction on α-hydroxy
ketones and 1,2-diones: To the solution of α-hydroxy ketones or 1,2-diones (1 mmol) in dry
dimethylformamide (DMF; 3 mL) indium metal (119 mg, 1.05 equiv), propargyl bromide (80%
propargyl bromide in toluene; (228 mg, 1.55 equiv); CAUTION: Lachrymatory) in DMF (1 mL)
and sodium iodide (230 mg, 1.55 equiv) were added sequentially and stirred at rt for 8-48 h.
After completion of the reaction (by TLC), 1N HCl solution (1 mL) was added to the reaction
mixture and stirred for 15 min. Then the reaction mixture was diluted with dichloromethane (20
mL). The DCM solution was washed with water (2 × 20 mL), brine (2 × 20 mL) and dried with
anhydrous sodium sulfate. Removal of the solvent resulted in the crude product which was
subjected to column chromatography using silica gel (100-200 mesh) and increasing amounts of
(2 to 5%) ethyl acetate (EtOAc) in hexanes to afford 1,2-diols or α-hydroxy ketones.
4.3a.(1RS,2SR)-1,2-Diphenylpent-4-yne-1,2-diol (3a):
OH
HO
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Light yellow semi solid; yield 76%; IR (KBr) νmax 3458, 3067, 2965, 2925, 2857, 1676, 1595,
1450, 1148, 973, 898, 761, 736 cm-1; 1H NMR (400 MHz, CDCl3 + CCl4) δ 7.18-7.10 (m, 8H),
6.99-6.94 (m, 2H), 4.85 (s, 1H), 3.12 (s, 2H), 2.89-2.85 (m, 2H), 1.93 (t, J = 2.6 Hz, 1H) ppm;
13C NMR (100 MHz, CDCl3 + CCl4) δ 141.1 (C) , 139.0 (C), 127.9 (CH) , 127.8 (CH), 127.6
(CH), 127.5 (CH), 127.4 (C), 126.6 (CH), 80.5 (acetylenic C), 79.3 (CH), 78.1 (acetylenic CH),
72.4 (C), 29.1 (CH2) ppm; HRMS (ESI) calcd for C17H16O2Na [M + Na]+ 275.1048, found
275.1048.
4.3b.(1RS,2SR)-1,2-Bis(4-chlorophenyl)pent-4-yne-1,2-diol (3b):
Light yellow solid: yield 72%; mp. 68-70 ºC; IR (KBr) νmax 3424, 3283, 2927, 1608, 1492, 1407,
1329, 1283, 1091, 1048, 654 cm-1; 1H NMR (400 MHz, CDCl3+ CCl4) δ 7.18 (d, J = 8.7 Hz,
2H), 7.12 (d, J = 8.5 Hz, 2H), 7.06 (d, J = 8.7 Hz, 2H), 6.91 (d, J = 8.4 Hz, 2H), 4.80 (s, 1H),
3.07 (br s, 2H), 2.84 (t, J= 2.3 Hz, 2H), 2.00 (t, J = 2.6 Hz, 1H). 13C NMR (100 MHz, CDCl3 +
CCl4) δ 139.3 (C), 137.2 (C), 134.0 (C), 133.7 (C), 129.2 (CH), 128.0 (CH), 128.0 (CH), 127.9
(CH), 79.8 (acetylenic CH), 78.5 (CH), 77.7 (C), 73.0 (acetylenic CH), 29.2 (CH3); HRMS (ESI)
calcd for C17H14Cl2O2Na [M + Na]+ 343.0263, found 343.0271.
4.3c.1RS,2SR)-1,2-Di(naphthalen-2-yl)pent-4-yne-1,2-diol (3c):
Light yellow semi solid; yield 77%; IR (KBr) νmax 3420, 3255, 2930, 1956, 1622, 1603, 1596,
1499, 1342, 1248, 1016, 849, 719, 664 cm-1; 1H NMR (400 MHz, CDCl3 + CCl4) δ 7.82-7.77 (m,
2H), 7.77-7.72 (m, 2H), 7.72-7.67 (m, 2H), 7.58 (d, J = 8.6 Hz, 1H), 7.49-7.40 (m, 4H), 7.29 (dd,
J = 8.7, 1.9 Hz, 1H), 7.12 (dd, J = 8.5, 1.7 Hz, 1H), 5.22 (s, 1H), 3.18 (s, 2H), 3.09-3.07 (m, 2H),
2.95 ( br s, 1H), 2.02 (t, J = 2.6 Hz, 1H) ppm; 13C NMR (100 MHz, CDCl3 + CCl4) δ 138.5 (C),
136.4 (C), 133.1 (C), 132.8 (C), 132.8 (C), 132.7 (C), 128.5 (CH), 128.2 (CH), 127.7 (CH),
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127.6 (CH), 127.3 (CH), 127.2 (CH), 127.0 (CH), 126.2 (CH), 126.1 (CH), 126.1 (CH), 126.07
(CH), 126.0 (CH), 125.8 (CH), 124.6 (CH), 80.2 (acetylenic C), 79.5 (CH), 78.5 (C), 72.6
(acetylenic CH), 29.2 (CH2) ppm; HRMS (ESI) calcd for C25H21O2 [M + H]+ 353.1536, found
353.1539.
4.3d.3-Phenylhex-5-yne-2,3-diol (3d):
HO
OH
CH3
Yellow semi solid; yield 81%; IR (KBr) νmax3400, 2929, 1629, 1492, 1446, 1389, 1186, 856,
765, 700, 645 cm-1; 1H NMR (400 MHz, CDCl3) δ 7.41 (d, J = 7.8 Hz, 2H), 7.34 (t, J = 7.6 Hz,
2H), 7.26 (dd, J = 8.3, 6.1 Hz, 1H),4.17-3.89 (m, 1H), 3.01 (dd, J = 16.9, 2.6 Hz, 1H), 2.93 –
2.74 (m, 2H), 2.37 (s, 1H), 1.94 (t, J = 2.5 Hz, 1H), 0.94 (d, J= 6.4 Hz, 3H). 13C NMR (100
MHz, CDCl3) δ 142.6 (C), 128.6 (CH), 127.8 (CH), 125.6 (CH), 80.1 (C), 75.9 (C), 72.2
(acetylenic CH), 69.3 (CH), 29.3 (CH2), 17.8 (CH3) ppm.
4.3e.4-Methylnon-1-yne-4,5-diol (3e):
HO
OH
Light yellow semi solid; yield 78%; IR (KBr) νmax 3423, 3307, 2947, 2118, 1664, 1457, 1069,
852, 784, 637 cm-1; 1H NMR (400 MHz, CDCl3) δ 4.89 (dd, J = 6.6, 1.3 Hz, 1H), 3.68 – 3.37 (m,
1H), 2.45 (dd, J= 18.2, 3.6 Hz, 3H), 2.07 (dd, J = 2.6, 2.2 Hz, 1H), 1.41 – 1.28 (m, 5H), 1.22 (d,
J= 10.7 Hz, 4H), 0.90 (dd, J= 8.2, 5.6 Hz, 4H);.13C NMR (100 MHz, CDCl3) δ 97.1 (C), 80.5
(CH), 76.0 (CH), 74.0 (CH), 71.5 (CH), 30.8 (CH2), 29.9 (CH2), 28.7 (CH2), 22.7 (CH2), 21.6
(CH3), 14.1 (CH3) ppm.
4.3f.(9RS,10RS)-9-(Prop-2-yn-1-yl)-9,10-dihydrophenanthrene-9,10-diol (18a):
13

ACCEPTED MANUSCRIPT
OH
OH
White semi solid; yield 89%; IR (KBr) νmax 3507, 3475, 3283, 3061, 2923, 2856, 1600, 1481,
1448, 1388, 1349, 1322, 1283, 1261, 1239, 1225, 1193, 1110, 1073, 1059, 984, 878, 842, 760,
735, 675, 658, 635 cm-1; 1H NMR (400 MHz, CDCl3) δ 7.72-7.63 (m, 4H), 7.42-7.32 (m, 4H),
5.03 (s, 1H), 3.17 (s, 1H), 2.96 (s, 1H), 2.78 (dd, J = 17.0, 2.7 Hz, 1H), 2.20 (dd, J = 17.0, 1.4
Hz, 1H), 2.03-1.99 (m, 1H) ppm; 13C NMR (100 MHz, CDCl3) δ 138.9 (C), 135.7 (C), 132.3
(C),132.0 (C), 128.7 (CH), 128.4 (CH), 128.3 (CH), 128.1 (CH), 125.2 (CH), 124.7 (CH), 124.0
(CH), 123.8 (CH), 80.0 (C), 75.5 (acetylinic C), 75.0 (CH), 72.8 (acetylinic C), 24.6 (CH2) ppm;
HRMS (ESI) calcd for C17H14O2Na [M + Na]+ 273.0891, found 273.0899.
4.3g.(4RS,5RS)-4-(Prop-2-ynyl)-4,5-dihydropyrene-4,5-diol (18b):
OH
OH
White solid; yield 85%; mp.146-147 ºC; IR (KBr) νmax: 3421, 3300, 3040, 1685, 1587, 1431,
1221, 1168, 1124, 1067, 834, 757, 728 cm-1; 1H NMR (400 MHz, CDCl3 + CCl4) δ 7.92 (d, J=
7.2 Hz, 1H), 7.86 (d, J= 7.2 Hz, 1H), 7.78 (t, J = 7.4 Hz, 2H), 7.71 (s, 2H), 7.57 (t, J= 7.6 Hz,
2H), 5.49 (s, 1H), 3.99 (s, 1H), 3.12 (dd, J= 17.1, 2.5 Hz, 1H), 2.34 (dd, J = 17.1, 2.5 Hz, 1H),
2.40 (t, J= 2.5 Hz, 1H) ppm; 13C NMR (100 MHz, CDCl3 + CCl4) δ 137.8 (C), 135.1 (C), 131.1
(C), 130.9 (C), 127.6 (CH), 127.1 (CH), 127.0 (CH), 126.8 (CH), 126.6 (CH), 126.5 (CH), 125.6
(C), 125.4 (C), 123.3 (CH), 122.7 (CH), 80.2 (C), 76.8 (acetylinic C), 75.8 (CH), 72.9 (acetylinic
C), 25.5 (CH2). ppm; HRMS (ESI) calcd for C19H14O2Na [M + Na]+ 297.0891, found 297.0894.
4.3h.(1RS,2RS)-1-(Prop-2-yn-1-yl)-1,2-dihydroacenaphthylene-1,2-diol (18c):
HO
HO
14

ACCEPTED MANUSCRIPT
White semi solid; yield 89%; IR (KBr) νmax 3293, 3270, 1489, 1410, 1363, 1332, 1280, 1248,
1157, 1089, 1071, 1027, 933, 912, 871, 776, 724, 641, 550 cm-1; 1H NMR (400 MHz, CDCl3) δ
7.81-7.77 (m, 2H), 7.61-7.53 (m, 4H), 5.54 (d, J = 6.8 Hz, 1H), 3.02 (dd, J = 16.8, 2.6 Hz, 1H),
2.99 (dd, J = 16.6, 2.6 Hz, 1H), 2.79 (s, 1H), 2.77 (s, 1H), 1.95 (t, J= 2.6 Hz, 1H);13C NMR (100
MHz, CDCl3) δ 143.8 (C), 141.2 (C), 135.6 (C), 131.0 (C), 128.7 (CH), 128.5 (CH), 125.6 (CH),
125.2 (CH), 120.8 (CH), 119.5 (CH), 84.9 (CH), 84.0 (C), 80.8 (acetylinic C), 72.1 (acetylinic
C), 27.5 (CH2) ppm; HRMS (ESI) calcd for C15H12O2Na [M + Na]+ 247.0735, found 247.0734.
4.3i.2-Phenylpent-4-yne-1,2-diol (20a):
HO
OH
Light yellow semi solid; yield 92%; IR (KBr) νmax 3400, 2929, 1629, 1492, 1446, 1389, 1186,
856, 765, 700, 645 cm-1; 1H NMR (400 MHz, CDCl3) δ 7.46-7.26 (m, 5H), 3.79-3.72 (m, 2H),
2.89-2.82 (m, 2H), 1.97 (t, J = 2.7 Hz, 1H) ppm; 13C NMR (100 MHz, CDCl3) δ 142.6 (C), 128.6
(CH), 127.8 (CH), 125.6 (CH), 80.1 (C), 75.9 (C), 72.2 (acetylenic CH), 69.3 (CH2), 29.3 (CH2)
ppm.
4.3j.2-(4-Chlorophenyl)pent-4-yne-1,2-diol (20b):
HO
OH
Cl
Brown liquid; yield; 76%; IR (KBr) νmax 3424, 3297, 2930, 2119, 1598, 1492, 1268, 1091, 827,
722, 646 cm-1; 1H NMR (400 MHz, CDCl3) δ 7.33 (d, J= 8.6 Hz, 1H), 7.29 – 7.23 (m, 1H), 7.18
(s, 2H), 4.90 (dd, J = 6.7, 2.7 Hz, 1H), 3.66 (d, J = 1.1 Hz, 2H), 2.71 (ddd, J= 50.1, 16.9, 2.6 Hz,
2H), 2.09 – 1.81 (m, 2H).; 13C NMR (100 MHz, CDCl3) δ 142.6 (C), 128.6 (CH), 127.8 (CH),
125.6 (CH), 80.1 (C), 75.9 (C), 72.2 (acetylenic CH), 69.3 (CH), 30.3 (CH2), 21.8 (CH3), 21.2
(CH3) ppm.
4.3k.2-(p-Tolyl)pent-4-yne-1,2-diol (20c):
15

ACCEPTED MANUSCRIPT
HO
OH
H3C
Yellow liquid; yield 73%; IR (KBr) νmax 3530, 3296, 2922, 2118, 1684, 1609, 1514, 1282, 1051,
854, 644 cm-1; 1H NMR (400 MHz, CDCl3) δ 7.92 (d, J = 8.2 Hz, 1H), 7.24 (d, J = 1.7 Hz, 1H),
7.22 – 7.16 (m, 1H), 7.09 (d, J = 8.1 Hz, 2H), 5.56 (s, 1H), 4.88 (s, 1H), 3.99 (dd, J = 9.7, 3.0
Hz, 2H), 2.84 (dtd, J = 30.1, 16.8, 2.7 Hz, 2H), 2.36 (s, 3H), 2.31 – 2.24 (m, 3H), 2.05 – 1.82 (m,
1H). ppm; 13C NMR (100 MHz, CDCl3) 144.4 (C), 138.6 (C), 137.2 (C), 130.4 (CH), 129.3
(CH), 129.1 (CH), 125.8 (CH), 125.9 (CH), 96.3 (C), 81.6 (C), 80.3 (C), 74.3 (CH), 71.9 (CH),
70.9 (CH), 30.9 (CH2), 22.1 (CH2), 21.2 (CH3) ppm.
4.3l.2-(4-Methoxyphenyl)pent-4-yne-1,2-diol (20d):
HO
OH
H3CO
Yellow liquid; yield 71%; IR (KBr) νmax 3530, 3296, 2922, 2119, 1684, 1609, 1514, 1282, 1051,
854, 644 cm-1; 1H NMR (400 MHz, CDCl3) δ 7.22 (d, J= 7.9 Hz, 1H), 6.84 (dd, J = 24.3, 8.5 Hz,
3H), 4.72 (s, 1H), 3.92 – 3.80 (m, 1H), 3.74 (d, J = 12.7 Hz, 3H), 2.30 (dd, J = 7.7 Hz, 1H), 2.19
– 1.89 (m, 2H), 1.25 (d, J= 4.5 Hz, 1H). 13C NMR (100 MHz, CDCl3) δ 159.3 (C), 132.3 (C),
131.9 (CH), 128.0 (CH), 113.9 (CH), 81.3 (C), 75.1 (CH), 73.4 (CH), 70.8 (CH), 55.2 (OCH3),
21.9 (CH2), 29.2 (CH2) ppm.
4.3m.(1RS,2SR)-1-Phenylpent-4-yne-1,2-diol (23) and (24):
OH
OH
OH
OH
Semi solid; The NMR data of the major isomer 24 was culled from the reaction mixture NMR;
IR (KBr) νmax 3398, 3294, 3063, 2922, 2854, 1602, 1452, 1417, 1217, 1070, 702 cm-1; 1H NMR
(400 MHz, CDCl3 + CCl4) δ 7.33-7.30 (m, 4H), 7.30-7.26 (m, 1H), 4.80 (d, J = 4.5 Hz, 1H), 3.93
(dt, J= 8.1, 4.6 Hz, 1H), 3.10 (s, 1H), 2.81 (s, 1H), 2.45-2.37 (m, 1H), 2.20-2.13 (m, 1H), 2.00 (t,
16

ACCEPTED MANUSCRIPT
J = 2.7 Hz, 1H) ppm; 13C NMR (100 MHz, CDCl3+ CCl4) δ 139.8 (CH), 128.6 (CH), 128.1
(CH), 126.7 (CH), 81.2 (CH), 75.5 (C), 73.4 (CH), 71.0 (CH), 21.8 (CH2) ppm; HRMS (ESI)
calcd for C11H12O2Na [M + Na]+ 199.0735, found 199.0733.
4.3n.(4RS,5SR)-2,2-Dimethyl-4-phenyl-5-(prop-2-yn-1-yl)-1,3-dioxolane 26 and 27:
O
O
O
O
8:2 ratio as a semi solid; The NMR data of the major isomer 26 was culled from the reaction
mixture NMR. IR (KBr) νmax: 3275, 3039, 2994, 2942, 1452, 1269, 1219, 1161, 1107, 1022, 897,
852, 652 cm-1; 1H NMR (400 MHz, CDCl3 + CCl4) δ 7.35-7.25 (m, 5H), 5.27 (t, J= 6.5 Hz, 1H),
4.55-4.47 (m, 1H), 1.84 (t, J = 2.7 Hz, 2H), 1.64 (s, 3H), 1.48 (s, 3H) ppm; 13C NMR (100 MHz,
CDCl3) δ 136.9 (C), 128.5 (CH), 128.2 (CH), 126.9 (CH), 108.9 (CH), 81.0 (C), 79.6 (CH), 77.6
(CH), 69.9 (CH), 27.8 (CH3), 25.3 (CH), 22.3 (CH2) ppm. HRMS (ESI) calcd for C14H16O2Na
[M + Na]+ 239.1048, found 239.1048.
4.4 General procedure for iodine mediated reaction to form furans from 1,2-
acetylenicdiols: To the solution of 1,2-acetylenicdiol (0.1 mmol) in 1,4-dioxane (1 mL), iodine
10 mol% (3 mg) was added and the resulting light violet colored solution was rt to reflux. After
completion of the reaction (12-24 h, TLC) 1,4-dioxane was evaporated in a rotovap and the
resulting crude product was diluted with dichloromethane (DCM, 20 mL). In some cases, the
reaction worked at rt or at 60 oC (see supplementary information for experimental details and
spectra of all the starting 1,2-acetylenicdiols and furan products). The DCM solution was washed
sequentially with hypo (0.1 mol in water, 2 × 20 mL), brine (2 × 20 mL) and then dried over
anhydrous sodium sulfate. Removal of DCM resulted in the crude product, which was purified
by column chromatography using silica (100-200 mesh) and hexane as eluent to afford
substituted furan derivatives.
4.4a.5-Methyl-2,3-diphenylfuran (5a):
17

ACCEPTED MANUSCRIPT
Colorless liquid; yield 90%; IR (KBr) νmax 3057, 3029, 2920, 2852, 1601, 1559, 1502, 1444,
1274, 1242, 1128, 1070, 1026, 998, 952, 912, 808, 762, 695, 672 cm-1; 1H NMR (400 MHz,
CDCl3) δ 7.50 (dd, J = 8.0, 1.0 Hz, 2H), 7.41-7.39 (m, 2H), 7.36-7.32 (m, 2H), 7.29-7.26 (m,
2H), 7.25-7.18 (m, 2H), 6.16 (d, J = 1.0 Hz, 1H), 2.39 (d, J = 1.0 Hz, 3H) ppm; 13C NMR (100
MHz, CDCl3) δ 151.4 (C), 146.9 (C), 134.9 (C), 131.6 (C), 128.7 (CH), 128.6 (CH), 128.4 (CH),
127.2 (CH), 127.1 (CH), 126.1 (CH), 123.3(C), 110.3 (CH), 13.7 (CH3) ppm; HRMS (ESI) calcd
for C17H15O [M + H]+ 235.1117, found 235.1108.
4.4b.2,3-Bis(4-chlorophenyl)-5-methylfuran (5b):
Colorless liquid; yield 88%; IR (KBr) νmax 3032, 2916, 2858, 1650, 1607, 1548, 1494, 1285,
1092, 831, cm-1; 1H NMR (400 MHz, CDCl3 + CCl4) δ 7.38 (d, J = 8.8 Hz, 2H), 7.30-7.27 (m,
4H), 7.22 (d, J = 8.8 Hz, 2H), 6.09 (d, J = 1.0 Hz, 1H), 2.37 (d, J = 0.9 Hz, 3H) ppm; 13C NMR
(100 MHz, CDCl3+ CCl4) δ 151.9 (C), 146.1 (C), 133.3 (C), 133.2 (C), 133.1 (C), 130.0 (CH),
129.8 (C), 129.1 (CH), 128.9 (CH), 127.3 (CH), 122.7 (C), 110.3 (CH), 13.8 (CH3) ppm; HRMS
(ESI) calcd for C17H14Cl2O2Na [M + Na]+ 325.0157, found 325.0159.
4.4c.5-Methyl-2,3-di(naphthalen-2-yl)furan (5c):
18

ACCEPTED MANUSCRIPT
Colorless liquid; yield 92%; IR (KBr) νmax 3053, 2916, 1669, 1627, 1597, 1573, 1506, 1434,
1355, 1271, 1230, 1174, 1017, 962, 894, 858, 818, 747, 707, 694 cm-1; 1H NMR (400 MHz,
CDCl3) δ 8.09 (s, 1H), 7.95 (s, 1H), 7.89-7.86 (m, 1H), 7.83-7.72 (m, 4H), 7.69 (d, J = 8.0 Hz,
1H), 7.60 (dd, J = 8.0, 1.7 Hz, 1H), 7.55 (dd, J = 8.0, 1.7 Hz, 1H), 7.52-7.48 (m, 2H), 7.46-7.42
(m, 2H), 6.34 (d, J = 1.0 Hz, 1H), 2.48 (d, J = 1.0 Hz, 3H) ppm; 13C NMR (100 MHz, CDCl3) δ
151.9 (C), 147.3 (C), 133.8 (C), 133.6 (C), 132.7 (C), 132.6 (C), 132.3 (C), 129.0 (C), 128.3
(CH), 128.2 (CH), 128.1 (CH), 128.0 (CH), 127.8 (CH), 127.7 (CH), 127.3 (CH), 127.2 (CH),
126.3 (CH), 126.0 (CH), 125.8 (CH), 124.7 (CH), 124.5 (CH), 123.8 (C), 110.6 (CH), 13.8
(CH3) ppm; HRMS (ESI) calcd for C25H19O [M + H]+ 335.1430, found 335.1415.
4.4d.2,5-dimethyl-3-phenylfuran (5d):24
Light yellow liquid; yield 65%; IR (KBr) νmax 3039, 2922, 2863, 1730, 1592, 1492, 1444, 1380,
1275, 1130, 1007, 926, 806, 762, 697, 615,526, 422 cm-1; 1H NMR (400 MHz, CDCl3) δ 7.23
(dd, J = 8.3, 2.5 Hz, 4H), 7.15 – 7.01 (m, 1H),5.97 (d, J = 6.3 Hz, 1H), 2.29 (d, J = 6.4 Hz, 3H),
2.17 (d, J = 5.7 Hz, 3H).; 13C NMR (101 MHz, CDCl3) δ 149.5 (C), 145.6 (C), 134.6 (C), 128.5
(CH), 127.4 (CH), 126.0 (CH), 121.5 (CH), 107.0(CH), 96.2 (CH), 13.4 (CH3), 13.0 (CH3) ppm.
4.4e.3-Butyl-2,5-dimethylfuran (5e):25
Dark brown liquid; yield 55%; IR (KBr) νmax 2929, 2864, 1601, 1456, 1265, 1069, 1015, 807,
748, 633 cm-1; 1H NMR (400 MHz, CDCl3) δ 6.04 (dd, J = 57.9, 11.7 Hz, 1H), 1.77 (s, 3H), 1.40
– 1.30 (m, 3H), 1.26 (d, J = 13.7 Hz, 3H), 0.99 – 0.76 (m, 6H). 13C NMR (100 MHz, CDCl3) δ
146.8 (C), 142.0 (C), 129.9 (C), 128.2 (C), 102.9 (CH), 31.0, (CH2), 29.8 (CH2), 28.7 (CH2),
27.9 (CH3), 22.7 (d, J = 15.7 Hz), 14.2 (CH3) ppm. HRMS (ESI) calcd for C10H16O [M +
H]+152.1201, found 152.1181.
4.4f.2-Methylphenanthro[9,10-b]furan (14):
19

ACCEPTED MANUSCRIPT
White solid;yield 78%; mp. 125-126 ºC (Reported mp. 125-126 ºC); IR (KBr) νmax 3058, 2923,
2852, 1610, 1579, 1517, 1449, 1349, 1328, 1260, 1235, 1158, 1101, 1033, 943, 802, 755, 722
cm-1; 1H NMR (400 MHz, CDCl3) δ 8.65 (d, J = 8.2 Hz, 2H), 8.29-8.24 (m, 1H), 8.02 (dd, J =
7.8, 1.3 Hz, 1H), 7.65-7.52 (m, 4H), 6.79 (d, J = 0.8 Hz, 1H), 2.55 (d, J = 0.7 Hz, 3H) ppm; 13C
NMR (100 MHz, CDCl3) δ 154.4 (C), 148.3 (C), 128.5 (C), 128.1 (C), 127.6 (C), 127.0 (CH),
126.9 (CH), 125.3 (CH), 125.0 (CH), 124.0 (CH), 123.7 (CH), 123.6 (CH), 122.5 (CH), 121.5
(C), 120.3 (CH), 102.6 (CH), 14.3 (CH3).ppm; HRMS (ESI) calcd for C17H13O [M + H]+
233.0961, found 233.0950.
4.4g.10-Methylpyreno[4,5-b]furan (2):
White solid; yield 76%; mp. 170-171 ºC; IR (KBr) νmax 1595, 1577, 1423, 1063, 1020, 937, 824,
800, 759, 711 cm-1; 1H NMR (400 MHz, CDCl3) δ 8.52 (dd, J = 7.6, 1.1 Hz, 1H), 8.31 (dd, J =
7.6, 1.0 Hz, 1H), 8.12-8.10 (m, 2H), 8.05-7.99 (m, 4H), 6.99 (s, 1H), 2.69 (s, 3H); 13C NMR (100
MHz, CDCl3) δ 154.6 (C), 148.9 (C), 132.1 (C), 131.9 (C), 128.0 (CH), 127.7 (CH), 126.9 (C),
126.1 (CH), 126.0 (CH), 124.2 (2 x CH), 123.1 (C), 122.7 (C), 122.2 (C), 121.8 (C), 121.0 (CH),
117.1 (CH), 103.0 (CH), 14.0 (CH3) ppm; HRMS (ESI) calcd for C19H13O [M + H]+ 257.0961,
found 257.0953.
4.4h.8-Methylacenaphtho[1,2-b]furan (15):
Yellow liquid; yield 58%; IR (KBr) νmax 3047, 2916, 2850, 1715, 1614, 1565, 1476, 1440, 1329,
1216, 1186, 1140, 1076, 1032, 923, 815, 766, 709, 658, 619 cm-1; 1H NMR (400 MHz, CDCl3) δ
20

ACCEPTED MANUSCRIPT
7.66 (d, J = 8.0 Hz, 2H), 7.58 (t, J = 7.5 Hz, 2H), 7.48-7.44 (m, 2H), 6.38 (s, 1H), 2.66 (s, 3H)
ppm; 13C NMR (100 MHz, CDCl3) δ 158.5 (C), 157.2 (C), 131.2 (C), 130.9 (C), 129.3 (C), 128.0
(C), 127.5 (CH), 127.4 (CH), 126.5 (CH), 126.4 (CH), 121.7 (CH), 118.4 (CH), 103.2 (C), 14.7
(CH3) ppm; HRMS (ESI) calcd for C15H10OK [M + K]+ 245.0639, found 245.0645.
4.4i.2-Methyl-4-phenylfuran (21a):
Solid;yield 82%; mp. 62-64 ºC (Reported mp. 64-68 ºC); IR (KBr) νmax 2921, 1606, 1549, 1445,
1125, 1076, 1029, 918, 807, 748, 692 cm-1; 1H NMR (400 MHz, CDCl3) δ 7.56 (s, 1H), 7.44 (d,
J = 7.6 Hz, 2H), 7.35 (t, J = 7.6 Hz, 2H), 7.26-7.21 (m, 1H), 6.29 (d, J = 1.0 Hz, 1H), 2.34 (d, J =
1.0 Hz, 3H) ppm; 13C NMR (100 MHz, CDCl3) δ 153.3 (C), 136.8 (CH), 133.1 (C), 128.9 (CH),
127.4 (C), 126.9 (CH), 125.9 (CH), 105.1 (CH), 13.7 (CH3) ppm.
4.4j.4-(4-Chlorophenyl)-2-methylfuran (21b):
Yellow liquid; yield 64%; IR (KBr) νmax 2924, 2857, 1579, 1513, 1454, 1285, 1177, 1042, 807,
644 cm-1; 1H NMR (400 MHz, CDCl3) δ 7.25-7.24 (d, J = 11.8 Hz, 2H), 7.18-7.16 (d, J= 11.8
Hz, 2H), 6.07 (s, 1H), 2.31 (s, 3H) ppm; 13C NMR (100 MHz, CDCl3) δ 150.9 (C), 142.5 (CH),
136.3 (C), 130.9 (CH), 129.5 (C), 122.9 (CH), 107.6 (CH), 13.7 (CH3) ppm.
4.4k.2-Methyl-4-(p-tolyl)furan (21c):
21

ACCEPTED MANUSCRIPT
Yellow liquid; yield 71%; IR (KBr) νmax 2924, 2857, 1579, 1513, 1454, 1285, 1177, 1042, 807,
644 cm-1; 1H NMR (400 MHz, CDCl3) δ 7.25-7.24 (d, J = 11.8 Hz, 2H), 7.18-7.16 (d, J = 11.8
Hz, 2H), 6.07 (s, 1H), 2.31 (s, 3H) ppm; 13C NMR (100 MHz, CDCl3) δ 150.9 (C), 142.5 (CH),
136.3 (C), 130.9 (CH), 129.5 (C), 122.9 (CH), 107.6 (CH), , 21.4 (CH3) 13.7 (CH3) ppm.
4.4l.4-(4-Methoxyphenyl)-2-methylfuran (21d):
Yellow liquid; yield 76%; IR (KBr) νmax 2926, 2848, 1672, 1579, 1513, 1454, 1285, 1177, 1028,
1005, 833, 644 cm-1; 1H NMR (400 MHz, CDCl3) δ 7.25-7.24 (d, J = 11.8 Hz, 2H), 7.18-7.16 (d,
J = 11.8 Hz, 2H), 6.07 (s, 1H), 3.81 (s, 3H), 1.26 (s, 3H) ppm; 13C NMR (100 MHz, CDCl3) δ
158.5 (C), 150.9 (C), 124.9 (C), 124.6 (CH), 114.5 (C), 107.6 (CH), 104.3 (CH), 55.3 (OCH3)
13.9 (CH3) ppm.
4.4m.2-Methyl-5-phenylfuran (25):
Colorless liquid; yield 88%; IR (KBr) νmax 3012, 2924, 1597, 1548, 1489, 1448, 1022, 739, 692
cm-1; 1H NMR (400 MHz, CDCl3 + CCl4) δ 7.55-7.49 (m, 2H), 7.24 (t, J = 7.8 Hz, 2H), 7.12-
7.08 (m, 1H), 6.42 (d, J = 3.2 Hz, 1H), 5.95-5.92 (m, 1H), 2.28 (d, J = 0.6 Hz, 3H)ppm; 13C
NMR (101 MHz, CDCl3) δ 152.5 (C), 151.9 (C), 131.4 (C), 128.7 (CH), 126.9 (CH), 123.5
(CH), 107.9 (CH), 106.0 (CH), 14.0 (CH3) ppm. HRMS (ESI) calcd for C11H10ONa [M + Na]+
181.0629, found 181.0610.
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5. Acknowledgement
H.S.P.R thanks UGC, UGC-SAP and DST-FIST for financial support. V.S thanks, UGC and S.K
thanks Pondicherry University for fellowship. We thank CIF, Pondicherry University and IISc,
Bangalore for recording some of the spectra.
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