Rhodium-Catalyzed Reaction of Diazoacetates, Thiols and Azodicarboxylates: An Unusual 1,2-Aza Shift from a Sulfonium Ylide

Abstract

A one-pot reaction of diazoacetates, thiols and azodicarboxylates in the presence of a dirhodium acetate catalyst gave N,S-ketals in good yields. This reaction proceeded via an unusual 1,2-aza shift from a sulfonium ylide intermediate.

Key words

one-pot reaction - diazo compounds - sulfonium ylides - N,S-ketals - rearrangement reaction

References and Notes

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• 12 Typical Procedure for the Reaction of Diazo Compounds with Thiols and DEAD To a refluxing CH₂Cl₂ (8 mL) solution of Rh₂(OAc)₄ (2.7 mg, 1 mol%), benzenethiol 2a (66.0 mg, 0.60 mmol) and DEAD (143.6 mg, 0.83 mmol) under argon atmosphere was added methyl phenyl diazoacetate (1b, 96 mg, 0.55 mmol) in CH₂Cl₂ (4 mL) over 1 h via a syringe pump. After comple-tion of the addition, the reaction mixture was cooled to r.t. Then, the solvent was removed. The crude product was purified by flash chromatography on silica gel by using 20% EtOAc-light PE as eluent to give a white solid 4a in 70% yield. Methyl 2-( N , N ′-Dicarboethoxyhydrazinyl)-2-phenyl-2-(phenylthio)acetate (4a) R _f = 0.22 (30% EtOAc-light PE); mp 126.5-128.4 °C. ¹H NMR (300 MHz, CDCl₃): δ = 8.08 (d, J = 7.2 Hz, 2 H), 7.20-7.39 (m, 8 H), 6.51 (s, 1 H), 4.27-4.34 (m, 2 H), 3.96-4.04 (m, 2 H), 3.66 (s, 1 H), 1.04-1.43 (m, 6 H). ¹³C NMR (75 MHz, CDCl₃): δ = 168.5, 156.6, 155.7, 137.9, 137.3, 130.2, 129.3, 128.6, 128.4, 127.9, 127.7, 81.7, 63.1, 62.2, 52.8, 14.5, 13.9. HRMS: m/z calcd for C₂₁H₂₄N₂O₆S₁: 455.1247; found: 455.1237 [M + Na]⁺

10

Crystal Structure Data for 4h. C₂₂H₂₆N₂O₇S, Mw = 462.51, colorless, Triclinic, P1, a = 10.343 (2), b = 10.796 (2), c = 11.630 (2) Å, α = 106.74 (2)°, β = 102.61 (2)°, γ = 101.02 (2)°, V = 1167.93 (46) ų, Z = 2, T = 287 (2) K, ρ _calcd = 1.315 Mg·m^-3, F(000) = 488, λ = 0.71073 Å, µ = 0.183 mm^-1, GOF = 0.977, R(F) = 0.0435 and wR(F)2 = 0.1061 for 4930 observed reflections, I > 4σ, 1.91° < θ < 25.50°. CCDC 299823 contains the supplementary crystallographic data for this paper. These data can be obtained free of charge via www.ccdc.cam.ac.uk/conts/retrieving.html [or from the Cambridge Crystallographic Data Centre, 12, Union Road, Cambridge CB21EZ, UK; fax [phone]; or deposit@ ccdc.cam.ac.uk].