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General Procedure
for the Synthesis of 2-Alkynylcyclo-alk-2-enol
3a-l Representative Procedure for 2-(Phenylethynyl)cyclohex-2-enol
(3f, Table 1, Entry 6)
2-Iodocyclohex-2-enol (1b, 1.0 mmol), Pd(PPh3)Cl2 (5 mol%),
and CuI (5 mol%) were placed in an oven-dried flask under
N2. Dry Et3N was added, and the resulting
suspension was magnetically stirred. Upon dropwise addition of phenylacetylene 2a (1.2 mmol), the mixture was stirred
at r.t. until TLC showed the disappearance of the starting 2-iodo-cyclohex-2-enol
(ca. 6 h). H2O (50 mL) was added to the reaction mixture,
and the residue was extracted into EtOAc (4 × 15 mL), and
the extract was dried over anhyd Na2SO4. Removal
of the solvent under reduced pressure gave the crude product, which
was further purified by column chromatography on silica gel using
EtOAc-PE (1:9) as eluent to afford pure product 3f (91%) as a brown oil. IR (CH2Cl2):
3383, 2928, 1592, 1053, 755 cm-¹. ¹H
NMR (500 MHz, CDCl3): δ = 1.60-1.62
(m, 1 H), 1.75-1.78 (m, 3 H), 1.87-1.90 (m, 1
H), 2.12-2.21 (m, 2 H), 4.26 (br s, 1 H), 6.30 (t, J = 4.6 Hz,
1 H), 7.28-7.29 (m, 3 H), 7.43-7.44 (m, 2 H). ¹³C
NMR (125 MHz, CDCl3): δ = 18.1, 26.0,
30.6, 66.9, 88.4, 89.3, 123.2, 124.2, 128.2, 128.3, 131.6, 137.8.
MS (EI): m/z = 198 [M+].
Anal. Calcd for C14H14O: C, 84.81; H, 7.12.
Found: C, 84.91; H, 7.09.
<A NAME="RG04809ST-15">15</A>
General Procedure
for the Synthesis of Fused Furans 4a-lRepresentative
Procedure for 2-Phenyl-4,5,6,7-tetrahydrobenzofuran (4f, Table 3,
Entry 6)
To a soln of 2-(phenylethynyl)cyclohex-2-enol
(3f, 1.0 mmol) in DCE (1 mL) under N2 was
added AuBr3 (5 mol%) and heated the reaction
mixture at 70 ˚C for 30 min. After completion
of the reaction as indicated by TLC, the reaction mixture was concentrated
under reduced pressure and purified by column chromatography over
silica gel (100-200 mesh) to afford pure product 4f (86%) as a colourless liquid. R
f
= 0.82
(EtOAc-PE, 1:9). IR (CH2Cl2): 2934,
2815, 2354, 1669, 1600, 1247, 760 cm-¹. ¹H
NMR (500 MHz, CDCl3): δ = 1.75-1.78
(m, 2 H), 1.84-1.89 (m, 2 H), 2.46 (t, J = 6.1
Hz, 2 H), 6.47 (s, 1 H), 7.20 (t, J = 7.6
Hz, 1 H), 7.35 (t, J = 7.6
Hz, 2 H), 7.62 (d, J = 6.9
Hz, 2 H). ¹³C NMR (125 MHz, CDCl3): δ = 22.2,
23.1, 23.2, 23.4, 106.1, 119.0, 123.3, 126.6, 128.6, 131.5, 150.9.
MS (EI): m/z = 221 [M+ + Na+].
Anal. Calcd for C14H14O: C, 84.81; H, 7.12.
Found: C, 84.75; H, 7.15.