9762
A. Tutar et al. / Tetrahedron 57 ,2001) 9759±9763
give colorless crystals, mp: 1068C <Lit. mp: 104.5±1058C)
<1.07 mg, 95%).
<25 mL acetone/5 mL H2O) was added to a stirred solution
of 1,1,3-tribromo-1H-indene <10) <2.75 g, 7.80 mmol) in
acetone <50 mL) over 5 min. The resulting mixture was
stirred magnetically at room temperature for 30 min. The
precipitated silver bromide was removed by ®ltration.
50 mL methylene chloride was added to organic phase
and washed with H2O <3£40 mL), and dried over MgSO4.
The solution was concentrated under reduced pressure.
Complete removing of the solvent should be avoided,
since the product decomposes. However, it is stable after
crystallization. Crystallization from CH2Cl2±petroleum
ether <1:1, 10 mL) in a refrigerator yielded 3-bromoinde-
none 12 <1.47 g, 90%) as yellow needles, mp 578C, <Lit
mp 57.5±588C16). nmax <KBr) 1716, 1538, 1365, 1245,
1075, 912, 762, 683, 599, 554, 413 cm21; dH <400 MHz,
CDCl3) 7.39 <dt, J7.5, 1.1 Hz, 1H), 7.34 <brd, J7.0 Hz,
1H), 7.26 <brt, J7.2 Hz, 1H) 7.12 <brd, J7.3 Hz, 1H),
6.14 <s, 1H, ole®nic); dC <100 MHz, CDCl3) 193.8, 148.6,
142.9, 133.6, 130.4, 127.34, 121.8, 121.3.
,b) Elimination of tetrabromide 8 with potassium tert-
butoxide. To a stirred solution of tetrabromide 8 <2.5 g,
5.8 mmol) in dry and freshly distilled THF <70 mL) was
added potassium tert-butoxide <0.76 g, 6.8 mmol). The
resulting reaction mixture was stirred 12 h at room tempera-
ture. The mixture was diluted with water <40 mL), the
aqueous solution was extracted with ether <60 mL), washed
with water <40£2 mL), and dried over MgSO4. After
removal of the solvent, the residue <pale-yellow oil) was
®ltered on a short silica gel column <15 g) eluted with
hexane. The product was crystallized <hexane±diethyl
ether: 1:2, 6 mL) to give pure 10 <1.67 g, 82%); [Found:
C, 30.60; H, 1.35. C9H5Br3 requires C, 30.64; H, 1.43%];
n
max <KBr) 3114, 1544, 1258, 1202, 951, 864, 780, 750, 704,
683, 647 cm21; dH <400 MHz, CDCl3) 7.7 <m, 1H), 7.4 <m,
2H), 7.3 <m, 1H), 6.85 <s, ole®nic); dC <100 MHz, CDCl3)
147.0, 139.8, 135.2, 130.0, 129.2, 124.1, 122.4, 121.1, 50.8;
MS m/z 350/352/354/356 <M1), 271/273/275 <M1, 2Br,
35), 192/194 <M1, 22Br, 15), 113 <M1, 23Br, 100).
4.2.7. Synthesis of 2,3-dibromo-1H-inden-1-one ,14). ,a)
Silver ion-promoted hydrolysis of pentabromoindane 9. A
solution of AgClO4 <5.55 g, 26.75 mmol) in aqueous
acetone <40 mL acetone/10 mL H2O) was added to a stirred
solution of 1,1,2,3,3-pentabromoindane <9) <3.15 g,
6.14 mmol) in acetone <100 mL) over 5 min. The resulting
mixture was stirred at room temperature for 30 min. The
precipitated AgBr was removed by ®ltration. To the organic
phase was added methylene chloride <60 mL) and organic
phase was washed with water <30£2 mL) and dried over
Na2SO4. After removal of the solvent, the residue was
crystallized from methylene chloride±hexane <1:1, 25 mL)
by standing in refrigerator to give 2,3-dibromo-1H-inden-1-
one <14), yellow needless, <1.75 g, 98%). mp 1208C. <Lit.
mp 1238C17).
4.2.4. Synthesis of 1,1,2,3-tetrabromo-1H-indene ,11). ,a)
Thermal dehydrobromination of pentabromide 9. Penta-
bromide 9 <1.51 g, 3.4 mmol) in a sealed glass-tube was
allowed to heat in silicon oil bath to 1208C for 30 min.
The dark-colored material was ®ltered through a short
Al2O3 <15 g) column eluted with hexane. After evaporation
of the solvent, the residue was crystallized from CH2Cl2±
hexane <1:3, 10 mL) at room temperature to give tetra-
bromoindene 11, mp 1248C <1.18 g, 93%).
,b) Base-induced elimination reaction of pentabromide 9.
To a stirred solution of pentabromide 9 <2.60 g, 5.1 mmol)
in dry and freshly distilled THF <50 mL) was added <0.66 g,
5.9 mmol) potassium tert-butoxide. The resulting reaction
mixture was stirred 12 h at room temperature. The mixture
was diluted with water <30 mL), and the aqueous solution
was extracted with ether <50 mL), washed with water
<30£2 mL), and dried over MgSO4. After removal of the
solvent, the oily residue was ®ltered on a short silica gel
column <10 g) eluted with hexane to give 11 <1.71 g, 78%);
[Found: C, 24.96; H, 0.90. C9H8Br4 requires C, 25.04; H,
0.93%]; nmax <KBr) 3048, 1460, 1238, 1171, 1118, 890, 770,
753, 692 cm21; dH <400 MHz, CDCl3) 7.7 <brd, 1H), 7.4 <m,
2H), 7.3 <m, 1H); dC <100 MHz, CDCl3) 145.9, 135.0,
133.9, 130.3, 129.1 124.8, 124.2, 120.8; 54.74; MS m/z
428/430/432/434/436 <M1), 349/351/353/355 <M1, 2Br,
25), 272/274/276 <M1, 22Br), 191/193 <M1, 23Br, 100),
113 <M1, 24Br, 71).
,b) Silver ion-promoted hydrolysis of 1,1,2,3-tetrabromo-
1H-indene 11. A solution of AgClO4 <1.27 g, 6.2 mmol) in
aqueous acetone <25 mL acetone/5 mL H2O) was added to a
solution of 1,2,3,3-tetrabromoindene <11) <1.30 g, 3.0
mmol) in acetone <100 mL) over 10 min. After stirring at
room temperature for 30 min, the precipitated AgBr was
removed by ®ltration. To the ®ltrate was added methylene
chloride <70 mL) and organic layer was washed with water
<40£2 mL) and dried over Na2SO4. After removal of the
solvent, the residue was crystallized from methylene
chloride±hexane <1:1, 25 mL) by standing in refrigerator
to give 14 <98%); [Found: C, 37.81; H, 1.45. C9H4Br2O
requires C, 37.54; H, 1.40%]; nmax <KBr) 1715, 1542,
1208, 1096, 752, 693, 657, 425 cm21; dH <400 MHz,
CDCl3) 7.39±7.35 <m, 2H), 7.45 <t, J7.5 Hz, 1H), 7.12
<d, J7.2, 1H); dC <100 MHz, CDCl3) 186.5, 146.34,
142.5, 134.4, 129.9, 129.0, 122.9, 122.4, 121.1.
4.2.5. Photobromination of 1,1,3-tribromo-1H-indene
,10). To a solution of 10 <120 mg 0.34 mmol) in CDCl3
<0.5 mL) in an NMR tube was added bromine <66 mg,
0.41 mmol). The mixture was irradiated by a projector
lamp <150 W) for 10 min. The residue obtained after
removal of the solvent was crystallized from CH2Cl2±petro-
leum ether to give 1,1,2,3,3-pentabromoindane 9 <162 mg,
93%).
4.2.8. Thermal decomposition of 3-bromo-1H-inden-1-
one ,12). Bromoindenone 12 <0.44 g) was heated in a sealed
glass-tube at 130±1358C for 5 h. The dark residue was
subjected to silica gel chromatography <40 g) eluting with
hexane. The ®rst fraction gave 14 90 mg, 30%.
The second fraction was identi®ed as 5-bromo-7H-
benzo[c]¯uoren-7-one ,13) <150 mg, 45%), mp 2208C
<Lit. mp 220±2218C17) red crystals from methylene
4.2.6. Synthesis of 3-bromo-1H-inden-1-one ,12). A solu-
tion of AgClO4 <3.60 g, 17.16 mmol) in aqueous acetone