Seven-Membered Heterocycles. III. Homoallylic Resonance and a Unique Sulfur Extrusion Reaction in Seven-Membered Sulfur Heterocycles^1-3

Abstract

This paper describes some observations made during a study directed toward the synthesis of benzo [6] thiepin.The synthesis and structure of 5-hydroxy-2-chloro-4,5-dihydrobenzo[b]thiepin (VII) and its acetate (VIII) are reported. Treatment of VII with p-toluenesulfonic acid produced an ester (XI). In rationalizing the origin of XI, homoallylic resonance stabilization of the intermediate carbonium ion becomes important. Since carbonium ions appeared to promote a ring contraction, the pyrolysis of VIII was studied. The pyrolysis products were -chloronaphthalene and 1,1'-naphthyl disulfide, which suggested the intermediate formation of 2-chlorobenzo [6] thiepin. A reaction of extruded sulfur and 2-chloronaphthalene is reported.A number of papers dealing with the preparation and properties of thiepin derivatives have appeared during the past decade; however, the synthesis of benzo[6]-

Sulfuryl Chloride Promoted gem-Dichlorination–Dehydrochlorination in Alkyl Benzothiazinylacetates: Synthesis of the Skeleton of Trichochrome Pigments

“…Sulfuryl chloride has been used for both gem-dichlorination of active methylene compounds and also for desulfurization reactions. 6,7 The reaction of benzothiazinylacetates 7a,b with sulfuryl chloride under reflux conditions was highly chemo-and stereoselective and directly delivered the chlorobenzothiazinylideneacetates 9a,b in more than 70% yield via the corresponding unisolable gem-dichloro intermediates 8a,b. The mixtures of E-and Z-isomers of 9a,b were inseparable by column chromatography on silica gel and their ratio was E/Z 1:19 by 1 H NMR.…”

“…IR (neat): 3393, 1638, 1582 cm -1 . 2, 118.9, 123.2, 123.9, 124.9, 126.7, 133.6, 158. 7,116.4,118.0,118.9,121.7,122.8,123.3,124.9,125.0,126.9,127.0,129.5,133.2,133.6,158.28,158.33. HRMS (ESI): m/z [M + Na] + calcd for C 16 H 9 O 2 N 2 BrNaS 2 : 426.9181; found: 426.9178.…”

Seven-membered heterocycles. VII. Synthesis and properties of 1-benzothiepin and its chlorinated derivatives

“…-Sulfuryl chloride (1.67 g, 12.3 mmol) in CH2C12 (10 ml) was added over a 10-min period to a stirred solution of 2,3-dihydro-l-benzothiepin9 (2.00 g, 12.3 mmol) in CH2C12 (15 ml) cooled to -78°. After the reaction mixture was stirred at -20°for 1 week, the solvent was removed and gave a mixture of cis-(10) and <ro»s-4,5-dichloro-2,3,4,5-tetrahydro-l-benzothiepin (11): nmr (CDCla) 7.70-7.08 (m, 4, aromatic H's), 5.90 [s, 1 (combined weight with Cs H of the trans isomer), Cs H, cis isomer], 5.50 [d, 1 (combined weight with Cs H of the cis isomer), Jc5_c4 = 8 Hz, Cs H, trans isomer], 4.65 [t, 1 (combined weight with C4 H of the trans isomer), Jc.-cz = 5 Hz, C4 H, cis isomer], 4.34 [double t, 1 (combined weight with the C4 H of the cis isomer), Ja-ci = 8, Jm-cs = 3.5 Hz, C4 H trans isomer], 3.36-2.07 (m, 4, -SCH2CH2-, both isomers). Comparison of the C5 H intensities for the cis and trans isomers showed a ratio of 34:66 cis:trans.…”

“…Fractional crystallization of the mixture of isomers from CHCla-hexane gave pure ds-12, mp 169-170°, ir (CHC13) 1330, 1320, 1300, 1160, 1130, 1120 cm"1 (-S02-), nmr (CDC13) 8.15-7.23 (m, 4, aromatic H's), 6.41 (s, 1, Cs ), 4.90 (m, 1, C4 ), 3.47-2.14 (m, 4, -S02CH2CH2-), and pure trans-13, mp 165-166°, ir (CHClg), 1330, 1325, 1305, 1160, 1140, 1125 cm"1 (-S02-), nmr (CDClg) 8.28-8.10 (m, 1, C9 H), 7.73-7.54 (m, 3, C6, C7, C8 H's), 5.59 (d, 1, JCt-c4 = 7.0 Hz, Cs ), 4.70-4.48 (m, 1, C4 ), 4.08-2.2 (m, 4, -S02CH2CH2-).…”

“…2,2-Dichloro-2,3-dihydro-1-benzothiepin (19).-Using the procedure described above for the preparation of 8, the mixture of 2,3-dihydro-l-benzothiepin6 (4.86 g, 30 mmol) and AT-chlorosuccinimide (9.6 g, 66 mmol) in CC14 (40 ml) was stirred with a Hershberg stirrer at room temperature for 4 days and afforded 6.8 (98%) of 2,2-dichloro-2,3-dihydro-l-benzothiepin (19) as a brown oil: ir (CC14) 3060 (w), 1740 (m), 1460 (m), 1425 (m), 1300 (w), 1230 (w), 1200 (w), 1150 (w), 1000 (w), 945 cm"1 (w); nmr (CC14) 5 7.67-7.08 (m, 4, aromatic H's), 6.90 (d, 1, /05_c4 = 11 Hz, CE H), 6.26 (d t, 1, JC4-cs = 11, Jc4-c, = 7 Hz, C4 H), 3.10 (d, 2, J -7 Hz, -SCCI2CH2-); mass spectrum (70 eV) m/e (rel intensity) 230 (3), 194 (24), 162 (23), 160 (26), 159 (26), 147 (6), 134 (100), 127 (10), 126 (9), 115 (57). Elemental analysis was performed on the corresponding sulfone (see following experiment).…”