Synthesis of Sulfonyl Azides via Lewis Base Activation of Sulfonyl Fluorides and Trimethylsilyl Azide

Abstract

A protocol for the efficient conversion of sulfonyl fluorides into sulfonyl azides through Lewis base activation is described. The in situ generated sulfonyl azides are efficient diazo-transfer agents, affording diazo compounds and primary azides in excellent yields.

Key words

sulfonyl azides - Lewis base - diazo-transfer - sulfonyl fluoride - SuFEx

• References and Notes

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There is literature precedent for the conversion of sulfonyl fluorides to sulfonyl azides using NaN₃ in MeCN on an extremely electrophilic substrate:
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Conversion of sulfonyl fluorides to sulfonyl azides using NaN₃ in wet acetone has been reported:
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• 24 Typical Procedure for the Synthesis of Compound 2a To a solution of 2-nitrobenzenesulfonyl fluoride (103 mg, 0.5 mmol) in MeCN (1 mL) was added DBU (22 μL, 0.15 mmol, 0.3 equiv) followed by TMSN₃ (50 μL, 0.375 mmol, 0.75 equiv). The resultant solution was stirred at room temperature for 15 min, then a further portion of TMSN₃ (50 μL, 0.375 mmol, 0.75 equiv) was added. The solution was stirred for a further 45 min, filtered through a silica plug, eluting with EtOAc (50 mL), and volatiles removed under reduced pressure to yield 2a as a white solid. (105 mg, 0.46 mmol, 92%). ¹H NMR (400 MHz, CDCl₃): δ = 8.49–8.46 (m, 2 H), 8.20–8.16 (m, 2 H). ¹³C NMR (101 MHz, CDCl₃): δ = 151.2, 143.7, 128.9, 124.9. IR (CHCl₃): 2134 cm^–1.
• 25 See the Supporting Information for more information.
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