Dynamics of Anilinium Radical Fragmentation Processes
J. Am. Chem. Soc., Vol. 120, No. 41, 1998 10685
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26: H NMR (CD3CN) 3.04 (s, 3H, NCH3), 4.60 (s, 2H, NCH2),
6.60-6.71 (m, 3H, aromatic), 7.11-7.20 (m, 2H, aromatic), 7.36 and
7.65 (ABq, J ) 8.3, 4H, aromatic); 13C NMR (CD3CN) 39.4 (NCH3),
56.7 (NCH2), 113.2, 117.5, 119.7, 128.5, 130.1, 133.3, 146.6 and 150.2
(aromatic), 180.1 (CN); IR 2919, 2360, 1599, 1506, 1347, 1251, 934,
749, 691; MS 223 (15), 222 (86), 221 (24), 120 (100), 116 (23), 106
(24), 105 (12), 91 (14), 77(35); HRMS calcd for C15H14N2 222.1157,
found 222.1159.
radical in photochemical reactions of 1,4-dicyanobenzene with
either tetra-n-butylammonium N-methyl-N-phenylglycinate or
â-N-methyl-N-phenylaminoethanol shows that the respective
decarboxylation and retro-aldol cleavage processes occur with
exceptionally high efficiencies. Second, in accord with the high
rates observed for aminium radical decarboxylation, tethered
cyclohexenone-R-aminocarboxylates undergo high-yielding
SET-promoted photocyclization reactions under both direct and
SET-sensitized conditions. Last, we have demonstrated how
the rates of aminium radical R-fragmentation correlate with
quantum efficiencies of SET-promoted reactions of tertiary
amines and amides. A study of photocyclization reactions of
N-(aminoethyl)- and (amidoethyl)phthalimides show that the
quantum yields for these SET-promoted processes vary with
the electrofugal group and nitrogen substituent in the manner
predicted on the basis of the LFP-determined R-fragmentation
rates.
Photoaddition of DCB to the Aminoalcohol 8. A deoxygenated
MeCN solution (100 mL) containing 8 (36 mg, 0.24 mmol), DCB (31
mg, 0.24 mmol), and tetrabutylammonium acetate (TBAA) (9.04 g,
30.0 mmol) was irradiated with Pyrex glass filtered light for 2 h. The
photolyzate was concentrated under reduced pressure to ca. 20 mL.
The mixture was diluted with water and extracted with ether. The
ethereal extracts were dried and concentrated in vacuo, and the residue
was subjected to column chromatography (silica gel, 20% ether/hexanes)
to yield 17 mg (32%) of 26 and 3 mg of an unknown with 15 mg
(41%) of 8 and 19 mg (63%) of recovered DCB.
Photochemistry of Aminoenone 30. A deoxygenated MeCN
solution (100 mL) containing 30 (150 mg, 0.33 mmol) was irradiated
with uranium glass filtered light for 4 h. The photolyzate was
concentrated to ca. 5 mL, diluted with water, and extracted with ether.
The ethereal extracts were dried and concentrated in vacuo. The residue
was subjected to preparative TLC separation (silica gel, 66% ether/
hexanes) to yield 34 mg (61%) of the spirocyclic amino ketone 32:
1H NMR 1.55-1.64 (m, 2H), 1.69-1.75 (m, 2H), 1.74-1.85 (m, 2H),
2.18-2.31 (m, 5H), 2.25 (s, 3H, NCH3), 2.34 (d, J ) 9.3, 1H), 2.46-
2.54 (m, 2H); 13C NMR 23.3 (C7), 36.9 (C4 or C6), 37.6 (C6 or C4),
41.0 (C8), 42.1 (NCH3), 46.9 (C5), 54.5 (C10), 55.7 (C3), 68.0 (C1),
210.6 (CdO); MS 167 (13), 130 (35), 109 (10), 96 (20), 70 (15), 58
(46), 57 (100); HRMS calcd for C10H17NO 167.1310, found 167.1311.
A MeOH solution (100 mL) containing 30 (150 mg, 0.33 mmol)
was irradiated with uranium glass filtered light for 5 h. Workup and
preparative TLC separation (silica gel, 66% ether/hexanes) furnished
32 mg (58%) of 32.
An MeCN solution (100 mL) containing 30 (150 mg, 0.33 mmol)
and DCA (8 mg, 0.033 mmol) was irradiated with uranium glass filtered
light for 4 h. Workup followed by preparative TLC separation (silica
gel, 66% ether/hexanes) provided 33 mg (59%) of 32.
A MeOH solution (20 mL) containing 30 (25 mg, 0.055 mmol) and
DCA (3 mg, 0.011 mmol) was irradiated with uranium glass filtered
light for 5 h. Workup followed by preparative TLC separation (silica
gel, 66% ether/hexanes) gave 6 mg (63%) of 32.
Photochemistry of Aminoenone 31. An MeCN solution (100 mL)
containing 31 (100 mg, 0.51 mmol) and TBAA (3.0 g, 10 mmol) was
irradiated with uranium glass filtered light for 7 h. The photolyzate
was concentrated under reduced pressure to give a residue which was
subjected to column chromatography (silica, ether). The ethereal eluent
was concentrated under reduced pressure to give a residue which was
subjected to preparative TLC separation (silica gel, 75% ethyl acetate/
hexanes) to yield 40 mg (47%) of 32.
A MeOH solution (20 mL) containing 31 (20 mg, 0.10 mmol) and
TBAA (1.5 g, 5 mmol) was irradiated with uranium glass filtered light
for 10 h. Workup and preparative TLC separation (silica gel, 66%
ether/hexanes) furnished 10 mg (62%) of 32.
An MeCN solution (100 mL) containing 31 (100 mg, 0.51 mmol),
TBAA (3.0 g, 10 mmol), and DCA (12 mg, 0.052 mmol) was irradiated
with uranium glass filtered light for 8 h. Workup followed by
preparative TLC separation (silica gel, 66% ether/hexanes) provided
54 mg (64%) of 32.
A MeOH solution (20 mL) containing 31 (20 mg, 0.10 mmol),
TBAA (1.5 g, 5 mmol), and DCA (2.5 mg, 0.011 mmol) was irradiated
with uranium glass filtered light for 9 h. Workup followed by
preparative TLC separation (silica gel, 66% ether/hexanes) gave 10
mg (58%) of 32.
Experimental Section
General Procedure. All reported reactions were run under a dried
nitrogen atmosphere. Unless otherwise noted, all reagents were
obtained from commercial sources and used without further purification.
Dimethyl sulfoxide and triethylamine were distilled from calcium
hydride. Anhydrous solvents were obtained by distillation from the
indicated reagents: ether (Na, benzophenone ketyl), tetrahydrofuran
(Na, benzophenone ketyl), methylene chloride (P2O5). Column chro-
matography was performed with silica gel (230-400 mesh), Florisil
(100-200 mesh) adsorbents, or alumina (neutral, 80-120 mesh).
Preparative TLC was performed on 20 × 20 cm plates coated with
silical gel. All compounds were isolated as oils and shown to be >90%
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pure by H and/or 13C NMR unless otherwise noted.
1H NMR and 13C NMR spectra were recorded by using CDCl3
solutions unless otherwise specified, and chemical shifts are reported
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in parts per million relative to residual CHCl3 at 7.24 ppm (for H
NMR) and 77.0 ppm (for 13C NMR). 13C NMR resonance assignments
were aided by the use of the DEPT technique to determine numbers of
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attached hydrogens, and H NMR coupling constants (J values) are
reported in hertz. Infrared spectra were obtained neat liquids unless
otherwise specified, and data are reported in units of cm-1. Low (MS)
and high (HRMS) mass spectra, reported as m/z (relative intensity),
were recorded by using electron impact ionization (EI) unless otherwise
specified as chemical ionization (CI) or fast atom bombardment
ionization (FAB).
Photochemical reactions were conducted by using an apparatus
consisting of a 450-W medium-pressure mercury lamp surrounded by
a Pyrex or uranium glass filter and within a quartz, water-cooled well
that was purged with O2-free N2 both before and during irradiation.
Photochemical reaction progress was monitored by gas chromatography,
TLC, or 1H NMR. The solvents used in the photoreactions were
spectrograde: MeCN (Baker) or MeOH (Baker). 1,4-Dicyanobenzene
(DCB) was purchased from Aldrich and recrystallized (CHCl3) prior
to use. 9,10-Dicyanoanthracene (DCA) was purchased from Eastman
Kodak and recrystallized from benzene.
Photoaddition of DCB to the Anilinocarboxylate 1. A deoxy-
genated MeCN solution (20 mL) containing 1 (20 mg, 0.049 mmol)
and DCB (6 mg, 0.049 mmol) was irradiated with Pyrex glass filtered
light for 20 min. The photolyzate was diluted with water and extracted
with ether. The ethereal extracts were dried and concentrated in vacuo,
and the residue was subjected to column chromatography (silica gel,
20% ether/hexanes) to yield 2 mg (30%) of N,N′-dimethyl-N,N′-
diphenylethylene-1,2-diamine (25) and 3 mg (27%) of N-(4-cyanoben-
zyl)-N-methylaniline (26) with 4 mg (55%) of recovered DCB.
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25: H NMR (CD3CN) 2.89 (s, 6H, 2NCH3), 3.51 (s, 4H, 2NCH2),
DCA-Sensitized Irradiation of 33. An MeCN solution (100 mL)
containing 33 (190 mg, 0.37 mmol) and DCA (21 mg, 0.09 mmol)
was irradiated with uranium glass filtered light for 10 h. The
photolyzate was concentrated under reduced pressure to give a residue.
This residue was dissolved in 10 mL of methanol and filtered. The
filtrate was diluted with water and extracted with ether. The ethereal
6.60-6.71 (m, 6H, aromatic), 7.12-7.21 (m, 4H, aromatic); 13C NMR
(CD3CN) 38.8 (NCH3), 50.1 (NCH2), 112.8, 116.8, 118.9 and 130.1
(aromatic); IR 2957, 2925, 2863, 1733, 1599, 1506, 1374, 747, 692;
MS 241 (3), 240 (15), 149 (22), 120 (100), 105 (12), 91 (5), 77 (10);
HRMS calcd for C16H20N2 240.1626, found 240.1626.