Studies on Photosensitized Release of Carboxylates
J . Org. Chem., Vol. 62, No. 18, 1997 6251
P h en a cyl tigla te: yield 2.135 g (94%) from 1.329 g of acid,
white solid; mp 40-42 °C; H NMR (CDCl3) δ 1.82 (d, J ) 7,
P h en a cyl N-t-Boc-p h en yla la n in e: yield 0.392 g (60%)
from 0.345 g of acid, white solid; mp 139-142 °C dec; 1H NMR
(CDCl3) δ 1.33 (s, 9H), 2.96 (dd, J 1 ) 9, J 2 ) 14, 1H), 3.29 (dd,
J 1 ) 4, J 2 ) 14, 1H), 4.52 (m, 1H), 5.44 (d, J ) 7, 2H), 5.58 (d,
J ) 8, 1H), 7.23-7.71 (m, 8H), 7.95 (d, J ) 7, 2H); 13C NMR
(CDCl3) δ 193.4, 173.7, 138.2, 135.2, 134.9, 130.5, 130.0, 129.5,
128.7, 127.8, 67.9, 56.0, 38.2, 28.5; EI-MS m/z (rel. intensity)
383 (M+, 0.1), 266 (52), 192 (24), 131 (14), 120 (22), 105 (62),
91 (29), 77 (19), 57 (100).
1
3H), 1.90 (s, 3H), 5.40 (s, 2H), 7.03 (q, J ) 7, 1H), 7.35-7.62
(m, 3H), 7.92 (d, J ) 7, 2H); 13C NMR (CDCl3) δ 192.5, 167.2,
138.5, 134.3, 133.6, 128.6, 127.8, 127.6, 65.9, 14.3, 11.9; EI-
MS m/z (rel. intensity) 218 (M+, 23), 188 (25), 118 (30), 105
(100), 91 (45), 81 (90), 77 (84), 65 (18), 55 (87), 51 (67).
P h en a cyl p h en yla ceta te: yield 4.890 g (96%) from 4.085
g of acid, yellowish white crystalline solid; mp 43-46 °C (lit.33,34
mp 50 °C); 1H NMR (CDCl3) δ 3.83 (s, 2H), 5.35 (s, 2H), 7.31-
7.60 (m, 8H), 7.90 (d, J ) 7, 2H); 13C NMR (CDCl3) δ 192.0,
171.0, 134.2, 133.8, 133.6, 129.4, 128.8, 128.6, 127.8, 127.2,
66.4, 40.9; EI-MS m/z (rel. intensity) 254 (M+, 2), 118 (30), 105
(100), 91 (34), 77 (18).
P h en a cyl N-t-Boc-4-ch lor op h en yla la n in e: yield 0.397
1
g (91%) from 0.344 g of acid, white solid; mp 101-102 °C; H
NMR (CDCl3) δ 1.40 (s, 9H), 3.12 (dd, J 1 ) 7, J 2 ) 14, 1H),
3.33 (dd, J 1 ) 6, J 2 ) 14, 1H), 4.75 (m, 1H), 4.99 (d, J ) 8),
5.31 (d, J ) 16, 1H), 5.52 (d, J ) 16, 1H), 7.24 (dd, J 1 ) 17, J 2
) 9, 4H), 7.47-8.67 (m, 3H), 7.92 (d, J ) 7, 2H); 13C NMR
(CDCl3) δ 191.4, 171.3, 134.7, 134.1, 132.9, 130.9, 129.0, 128.7,
127.8, 66.4, 54.1, 37.6, 28.3; FAB-MS m/z (rel. intensity) 418
(M + H, 1), 364 (1), 362 (3), 200 (2), 198 (4), 156 (12), 154 (45),
119 (8), 105 (17), 77 (10), 57 (100), 55 (26).
P h en a cyl 2-n itr op h en yla ceta te: yield 4.818 g (84%) from
3.633 g of acid, yellow crystals; mp 92-94 °C; 1H NMR (CDCl3)
δ 4.21 (s, 2H), 5.36 (s, 2H), 7.0-8.2 (m, 9H); 13C NMR (CDCl3)
δ 191.7, 169.4, 148.6, 134.0, 133.8, 133.5, 133.4, 129.2, 128.7,
127.6, 125.1, 66.4, 39.1; CI-MS m/z (rel. intensity) 300 (M +
1, 2), 136 (19), 118 (51), 105 (100), 92 (16), 77 (92).
P h en a cyl N-t-Boc-glycin e: yield 1.482 g (94%) from 1.237
P h en a cyl 2-m eth oxyp h en yla ceta te: yield 2.312 g (87%)
from 1.997 g of acid, yellow oil; 1H NMR (CDCl3) δ 3.72 (s,
3H), 3.78 (s, 2H), 5.23 (s, 2H), 6.78-6.91 (m, 2H), 7.20-7.47
(m, 5H), 7.79 (d, J ) 7, 2H); 13C NMR (CDCl3) δ 191.9, 170.8,
157.2, 133.9, 133.3, 130.6, 128.4, 128.3, 127.3, 122.3, 120.1,
110.2, 65.9, 55.0, 35.0; EI-MS m/z (rel. intensity) 284 (M+, 66),
148 (89), 121 (91), 105 (100), 91 (90), 77 (80), 66 (61), 51 (66).
P h en a cyl 4-br om op h en yla ceta te: yield 1.543 g (83%)
from 1.333 g of acid, white solid; mp 80-82 °C; 1H NMR
(CDCl3) δ 3.78 (s, 2H), 5.36 (s, 2H), 7.24 (d, J ) 8, 2H), 7.45-
7.65 (m, 5H), 7.89 (d, J ) 7, 2H); 13C NMR (CDCl3) δ 191.8,
170.5, 134.1, 133.9, 132.5, 131.7, 131.1, 128.9, 127.7, 121.3,
66.4, 40.2; EI-MS m/z (rel. intensity) 334 (M + 2, 2), 332 (M+,
2), 197 (63), 195 (63), 171 (61), 169 (61), 118 (2), 105 (100), 90
(51), 86 (22), 84 (30), 77 (77), 63 (22), 50 (48).
1
g of acid, white solid; mp 60-62 °C; H NMR (CDCl3) δ 1.46
(s, 9H), 4.12 (d, J ) 5, 2H), 5.14 (s, 1H), 5.41 (s, 2H), 7.48-
7.64 (m, 3H), 7.89 (d, J ) 7, 2H); 13C NMR (CDCl3) δ 191.5,
169.9, 155.6, 134.0, 128.8, 127.7, 79.9, 66.4, 42.2, 28.2; CI-MS
m/z (rel. intensity) 294 (M + 1, 3), 238 (19), 194 (16), 118 (18),
105 (100), 93 (13), 77 (15), 58 (62).
P h en a cyl N-t-Boc-Ile-Gly: yield 0.129 g (40%) from 0.136
g of acid, white solid; mp 136 °C dec; 1H NMR (CDCl3) δ 0.90
(m, 6H), 1.13 (m, 3H), 1.41 (s, 9H), 3.95 (m, 1H), 4.12 (dd, J 1
) 4, J 2 ) 6, 2H), 5.46 (s, 2H), 7.5-7.7 (m, 3H), 7.98 (d, J ) 7,
2H); 13C NMR (CDCl3) δ 173.2, 170.5, 135.0, 130.0, 128.8, 67.8,
41.4, 38.2, 28.6, 25.4, 15.9, 11.8; CI-MS m/z (rel. intensity) 407
(M + 1, 1), 406 (M+), 333 (22), 308 (18), 228 (35), 215 (37), 186
(100), 105 (20), 86 (34), 77 (12).
P h otolysis of P h en a cyl Ester s. The phenacyl esters (∼4
× 10-4 mol) were photolyzed for 2 h (16 h in the case of
2-nitrophenylacetate ester) in the presence of a large excess
(∼2.5 × 10-3 mol) of the sensitizer in 150 mL of acetonitrile
as the solvent. Corex filter was used in each case (Pyrex filter
was used when TMPD was used as the electron donor). The
conversion rate was analyzed using HPLC. The products were
dissolved in dichloromethane, and the acid was extracted into
the aqueous layer with dilute NaOH or NaHCO3 solution. The
aqueous layer was then acidified with HCl and the acid
extracted with dichloromethane. The organic layer was dried
over MgSO4, and the solvent was evaporated to yield the acid
which was then weighed and analyzed by 1H NMR and
compared to the 1H NMR of the authentic acid. Samples of
all the authentic acids were obtained from commercial sources.
P h en a cyl ben zoa te: yield 1.738 g (72%) from 2.00 g of
1
acid, white solid; mp 118-120 °C (lit.35 mp 117-120 °C); H
NMR (CDCl3) δ 5.57 (s, 2H), 7.42-7.65 (m, 6H), 7.96 (d, J )
7, 2H), 8.14 (d, J ) 7, 2H); 13C NMR (CDCl3) δ 192.0, 166.0,
134.3, 133.8, 133.3, 130.1, 129.9, 129.4, 128.8, 127.8, 66.4; EI-
MS m/z (rel. intensity) 240 (M+, 0.3), 118 (26), 105 (100), 78
(88).
P h en a cyl 4-h yd r oxyben zoa te: (CH3CN) yield 50%, yel-
low solid; mp 184-186 °C; 1H NMR (CDCl3-DMSO-d6) δ 5.60
(s, 2H), 6.88 (d, J ) 9, 2H), 7.51-7.70 (m, 3H), 7.92 (d, J ) 9,
2H), 7.99 (d, J ) 7, 2H), 9.53 (s, 1H); 13C NMR (CDCl3-DMSO-
d6) δ 191.1, 163.7, 160.8, 132.6, 132.2, 130.2, 127.3, 126.1,
118.4, 113.8, 64.8; EI-MS m/z (rel. intensity) 257 (M + 1, 3),
256 (M+, 15), 122 (8), 121 (93), 119 (1), 118 (7), 106 (8), 105
(100), 93 (10), 77 (18), 66 (12), 53 (5).
P h en a cyl m a n d ela te: yield 5.052 g (94%) from 3.393 g of
1
acid, white solid; mp 78-80 °C (lit.36 mp 84-84.5); H NMR
Ack n ow led gm en t. This work was supported in part
by the National Science Foundation and the University
of Maryland Graduate Research Board (GRB). We
thank Professor J . P. Y. Kao for helpful advice.
(CDCl3) δ 3.70 (d, J ) 5, 1H), 5.29 (d, J ) 16, 1H), 5.43 (d, J
) 16, 1H), 5.42 (s, 1H), 7.20-7.65 (m, 8H), 7.83 (d, J ) 7, 2H);
13C NMR (CDCl3) δ 191.2, 173.0, 137.9, 134.0, 128.9, 127.7,
126.9, 73.1, 67.1; CI-MS m/z (rel. intensity) 271 (M + 1, 2),
253 (55), 120 (96), 107 (85), 105 (100), 91 (59), 77 (92).
Su p p or tin g In for m a tion Ava ila ble: 1H NMR of all the
phenacyl esters (11 pages). This material is contained in
libraries on microfiche, immediately follows this article in the
microfilm version of the journal, and can be ordered from the
ACS; see any current masthead page for ordering information.
(33) Vijayaraghavan, S. T.; Balasubramanian, T. R. J . Organomet.
Chem. 1985, 282, 17-22.
(34) Shunmugasundaram, A.; Rajkumar, M. Indian J . Chem. 1986,
25A, 71-73.
(35) Moreland, W. T. J . Org. Chem. 1956, 21, 820-821.
(36) Rather, J . B.; Reid, E. E. J . Am. Chem. Soc. 1919, 41,75-83.
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