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General Experimental
Procedure
To a CH2Cl2 soln (3
mL/mmol of 1) of 2 (1.5
mmol) and 1 (2.25 mmol) was added TiCl4 (2.25
mmol) at -78 ˚C. The solution was allowed
to warm to 20 ˚C within 20 h. To the solution
was added HCl (10%, 25 mL). The organic and the aqueous
layer were separated and the latter was extracted with CH2Cl2 (3 × 20
mL). The combined organic layers were dried (Na2SO4),
filtered, and the filtrate was concentrated in vacuo, and the residue
was purified by chromatography (SiO2, EtOAc-n-heptane = 1:9).
4-Methoxy-6-methyl-2-(3-tolylsulfanyl)benzoic
Acid Methyl Ester (3b)
Starting with 1a (2.25
mmol), 2b (1.5 mmol), and TiCl4 (2.25
mmol), 3b was isolated as a yellow oil
(226 mg, 50%). ¹H NMR (250 MHz, CDCl3): δ = 2.25
(s, 3 H, CH3), 2.30 (s, 3 H, CH3), 3.69 (s,
3 H, OCH3), 3.87 (s, 3 H, OCH3), 6.57-7.39
(m, 6 H, Ar). ¹³C NMR (63 MHz, CDCl3): δ = 20.4 (CH3),
21.2 (CH3), 51.9 (OCH3), 55.2 (CH3O),
114.1, 114.5, (CHAr), 126.9, 128.3 (C), 129.4, 131.5,
132.1, 133.0 (CHAr), 138.3, 139.1, 140.1, 146.9, 168.8
(C). IR (KBr): ν = 2998 (w), 2947 (w), 2834 (w),
2735 (w), 2570 (w), 1724 (s), 1589 (s), 1564 (m), 15560 (m), 1471
(m), 1426 (m), 1380 (w), 1302 (m), 1264 (s), 1217 (s), 1187 (m),
1136 (s), 1090 (s), 1047 (s), 998 (m), 960 (m), 776 (s), 691 (s),
608 (m). MS (EI): m/z (%) = 302
(100) [M+], 272 (11), 271
(61), 270 (21), 269 (86), 256 (18), 255 (49),228 (17), 227 (13),
184 (15), 121 (3), 91 (4), 65 (5). HRMS (EI): m/z calcd
for C17H18O2O3S [M+]:
302.09712; found: 302.097152.