An Expeditious Synthesis of cis-2-(Aroylmethyl)-4-phenylthiochromans by Iodine-Catalyzed Combination of Thiophenol with Cinnamylidene­acetophenones

Abstract

Cinnamylideneacetophenones have been found to undergo facile cyclocondensation with thiophenol in dichloromethane under iodine-catalyzed conditions yielding cis-2-(aroylmethyl)-4-phenylthiochromans in very good to excellent yield. The structures of the products have been established from their spectral data as well as X-ray crystallographic studies on one of them.

Key words

thiophenol - cinnamylideneacetophenones - iodine - cis-2-(aroylmethyl)-4-phenylthiochromans

• References and Notes

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• 9 Representative Example of Iodine-Catalyzed Cyclocondensation of Cinnamylideneacetophenones 1 with Thiophenol: Synthesis of cis-2-(Benzoylmethyl)-4-phenylthiochroman (2a)To a mixture of cinnamylideneacetophenone^8,12 (1a, 234 mg, 1 mmol) and thiophenol (110 mg, 1 mmol) in anhyd CH₂Cl₂ (30 mL) iodine (64 mg, 0.25 mmol) was added, and the reaction mixture was refluxed. When the reaction was complete after 3 h, the reaction mixture was diluted with CH₂Cl₂ (25 mL), and the resulting solution was washed with aq Na₂S₂O₃ solution (5%, 2 × 25 mL) and H₂O (2 × 25 mL), successively. The solid material obtained after removal of CH₂Cl₂ showed one TLC spot, and it was purified further by passing through a silica gel (100–200 mesh) column [eluent: PE–EtOAc (90:10)] followed by crystallization from CHCl₃–PE. cis-2-(Benzoylmethyl)-4-phenylthiochroman (2a) thus obtained gave the following analytical and spectral data. Compound 2a: Colorless needles, mp 116 °C, IR (KBr): 1683 (C=O), 1581, 1468, 1392, 1360, 1244, 1208, 1177, 1067, 980, 817, 746 cm^–1. ¹H NMR (300 MHz, CDCl₃): δ = 2.09 (dt, J = 13.2, 11.6 Hz, 1 H, H-3_ax), 2.60 (dt, J = 13.2, 3.8 Hz, 1 H, H-3_eq), 3.32 (d, J = 6.8 Hz, 2 H, CH₂CO), 4.15–4.27 (m, 2 H, H-2 and H-4), 6.70 (br d, J = 7.8 Hz, 1 H, H-8), 6.92 (dt, J = 7.8, 1.4 Hz, 1 H, H-6), 7.09 (br t, J = 7.7 Hz, 1 H, H-7), 7.18 (dd, J = 7.8, 1.3 Hz, 1 H, H-5), 7.24–7.40 (m, 5 H, ArH), 7.47–7.52 (m, 2 H, ArH), 7.61 (tt, J = 7.4, 1.2 Hz, 1 H, para proton of COPh), 7.95–7.98 (m, 2 H, ortho protons of COPh). ¹³C NMR (75 MHz, CDCl₃): δ = 36.7, 39.5, 45.3, 46.6, 124.2, 126.4, 126.5, 126.7, 128.1, 128.67, 128.69, 129.4, 133.4, 133.6, 136.6, 137.7, 144.5, 197.0. Anal. Calcd (%) for C₂₃H₂₀SO: C, 80.19; H, 5.85. Found: C, 79.93; H, 5.96. TOFMS [ES⁺]: m/z calcd for C₂₃H₂₀SO [M + Na]⁺: 367.12; found: 367.20.Other compounds of this series, 2b–f (Table 1), were synthesized in the same way.
• 10 Crystallographic Data Collection and RefinementA suitable single crystal of compound 2b was mounted on a thin glass fiber with commercially available super glue. X-ray single-crystal data collection was performed at r.t. using Bruker APEX II diffractometer, equipped with a normal focus, sealed tube X-ray source with graphite monochromated Mo Kα radiation (λ = 0.71073 Å). The data were integrated using SAINT program, and the absorption corrections were made with SADABS. All the structures were solved by SHELXS 97 using direct method and followed by successive Fourier and difference Fourier synthesis. Full-matrix least-squares refinements were performed on F using SHELXL-97 with anisotropic displacement parameters for all nonhydrogen atoms. All the hydrogen atoms were fixed geometrically by HFIX command and placed in ideal positions. All calculations were carried out using SHELXL 97, SHELXS 97, PLATON v1.15, ORTEP-3v2, and Win GX system Ver-1.80. X-ray Data for C₂₃H₁₉ClOSMonoclinic; space group, P21/c, a = 16.0953(7)Å, b = 6.0206(3)Å, c = 20.4344(9)Å, β = 107.472(3)°; V = 1888.81(15) ų; Z = 4; ρ _calcd, 1.332 g·cm^–3; M = 378.90; μ(Mo Kα), 0.322 mm^–1; F(000), 792; θ _min–max = 1.3°–27.7°; total data, 29465; unique data, 4376 (R _int = 0.070); data (I > 2σI), 2731; final R, 0.0466; Rw, 0.1553; GOF, 1.05; max and min residual electron densities, 0.16 and –0.26 eÅ^–3, respectively. CCDC-860032 contains the supplementary crystallographic data for this paper. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data
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