Trimethylsilyl azide (TMSN3): A versatile reagent in organic synthesis

Abstract

(A) Polystyrene-supported ammonium fluoride (Amberlite IRA900F) is an excellent polymer-supported organocatalyst which has been used for the aza-Michael azidation of α,β-unsaturated ketones with TMSN, under solvent-free conditions with good to excellent yields. The catalyst was recycled and reused in four more runs without loss of its efficiency and activity. 15 (Chemical Equation Presented) (B) Regio- and stereoselective bromoazidation of alkenes was carried out using N-bromosuccinimide (NBS) and TMSN3 as bromine and azide source with good yields. Zinc triflate [Zn(OTf)2] was an efficient catalyst for the synthesis of anti-1,2-bromoazide with high selectivity.16 Also, bromoazidation of α,β-unsaturated carbonyl compounds has been performed with Yb(OTf)3 as catalyst.17 (Chemical Equation Presented) (C) Tetrabutylammonium fluoride (TBAF) has been utilized in the [3+2] cycloaddition of TMSN3 to variously substituted 3-nitrocoumarins18 and nitroethenes19 under solvent-free conditions in high yields. This approach is defined as an environmentally benign protocol for accessing a new class of fused triazoles. (Chemical Equation Presented) (D) Asymmetric ring-opening of the epoxides by TMSN3 in the presence of a salen-Al complex as chiral Lewis acid catalyst is demonstrated. The results revealed high enantioselectivity for the synthesis of trans-3-hydroxy-4-azidooxides from achiral epoxyphenylphospholane oxide.20 (Chemical Equation Presented) (E) Vaccaro and co-workers described a [3+2] cycloaddition of organic nitriles with TMSN, under mild conditions affording 80-97% yields. TBAF was an efficient catalyst in the solvent-free synthesis of 5-substituted 1H-tetrazoles. 21 Also dibutyltin oxide [Bu2Sn(O)] can be used for this reaction.22 (Chemical Equation Presented) (F) Yamamoto and co-workers reported a one-pot procedure for the regioselective synthesis of allyltriazides via three-component coupling reaction between non-activated terminal alkynes23 or silylacetylenes,24 allyl carbonate and TMSN3. The palladium/copper bimetallic catalyst was successfully applied for the formation of 1-allyl-1,2,3-triazoles. (Chemical Equation Presented) (G) Trimethylsilylation of a wide variety of alcohols, phenols and diols were performed under neat conditions with TMSN3. Tetrabutylammonium bromide (TBABr) was an efficient catalyst that activated the silicon atom towards nucleophilic attack.25 (Chemical Equation Presented) (H) The synthesis of α-alkoxy azides was carried out in a one-pot reaction of the aromatic and aliphatic aldehydes or ketones with alkoxytrimethylsilane and TMSN3. This procedure was promoted using iron(III) chloride as an inexpensive and commercially available catalyst under mild conditions with excellent yield.26 (Chemical Equation Presented). © Georg Thieme Verlag Stuttgart.