ORGANIC PREPARATIONS AND PROCEDURES INTERNATIONAL
3
nitrogen cooled trap was employed to condense the BF3 gas. Resublimation gave 20.0 g
(46%) of 2 as a colorless solid (mp 66–67 ꢀC). Recrystallization from 50% ethanol gave
white crystals mp 67–68 ꢀC (lit.23 mp 69–70 ꢀC). The overall yield from 2-naphthyl-
amine was 38%.
1-(Trimethylsilyl)pyrrole (3)20
A stirred mixture of freshly distilled pyrrole (16) (115 g, 1.7 mol), 1,1,1,3,3,3-hexame-
thyldisilazane (39) (152 g, 0.94 mol) and a catalytic amount of ammonium sulfate was
brought to reflux. After 25 h, the mixture was cooled and washed with water (7 x
150 mL) to remove much of the unreacted pyrrole. The organic phase was then dried
over Na2SO4 and fractionally distilled to give 121.1 g (51%) of 3 as a colorless liquid, bp
151–152 ꢀC (lit.20 bp 151–152 ꢀC); NMR (CDCl3) d 6.79 (broad s, 2), 6.35 (broad s, 2),
0.40 (s, 9); IR (NaCl neat) 2990, 1465, 1257, 1188, 1080, 1045, 943, 835, 725 cm.–1
1,4-Dihydrophenanthrene-1,4-imine (4)
To magnesium turnings (1.48g, 0.061 mol) in dry THF (7 mL) was added a small amount of
1-bromo-2-fluoronaphthalene (2) (ca. 0.5 g). To effect Grignard initiation it was necessary to
add a few drops of 1,2-dibromoethane. With the Grignard underway and heated to reflux, a
mixture of the remaining 1-bromo-2-fluoronaphthalene (2) (for a total of 8.01g, 0.036 mol)
and freshly distilled 1-(trimethylsilyl)pyrrole (3) (9.92g, 0.071 mol) in dry THF (40mL) was
added dropwise to the Grignard reaction with stirring and from a pressure-equalizing drop-
ping funnel over 1.5 h. After complete addition, the reaction mixture was stirred at reflux for
8 h, then cooled and the THF was replaced with ethyl ether. This ethereal solution was then
extracted with 5% aqueous HCl (7 x 150 mL). The combined aqueous extracts were basified
with the addition of conc aqueous KOH and back-extracted with ether (5 x 100 mL). The
combined ethereal extract was dried (MgSO4) and concentrated to dryness to yield 4.28g
(62%) of 4 as brown oil, which was used directly in the next step; NMR (CDCl3) d 7.50 (m,
6), 6.99 (s, 2 vinyl protons, 5.35 (s, 1-bridgehead proton), 4.96 (s, 1-bridgehead proton), 3.11
(s, 1-exchangeable NH); HRMS: Calcd for C14H11N: 193.0891; Found: 193.0928; Calcd for
C1313C1H11N; 194.0925; Found: 194.0941. A picrate of 4 was prepared in the usual fashion
from picric acid,24 and recrystallized from EtOH, mp 203-204 ꢀC dec.
Anal. Calcd for C20H14N4O7: C, 56.88; H, 3.34; N, 13.27; Found: C, 56.69, H, 3.43;
N 13.44.
Phenanthrene (1)
To 1,4-dihydrophenanthrene-1,4-imine (4) (0.716 g, 3.72 mmol) in benzene (40 mL) was
added iso-amyl nitrite (0.48 g, 4.1 mmol). The mixture was warmed to 50 ꢀC and the
progress of the reaction followed by TLC (hexane: EtOAc, 8:2). After complete reaction,
the solution was concentrated to dryness and redissolved in CH2Cl2 (40 mL). To this
solution was added finely ground CaCl2 (0.90 g, 8.17 mmol) and a small amount of
absolute ethanol (0.5 mL) with stirring. After 12 h the solution was filtered and concen-
trated to yield 0.603 g (86%) of crude 1. Sublimation at 85 ꢀC (0.3 Torr) afforded 0.546 g