Trimethylsilyldiazomethane

Abstract

(A) Trimethylsilyldiazomethane (TMSCHN 2) reacts rapidly with carboxylic acids in benzene or toluene in the presence of methanol, at room temperature, to afford the methyl esters in very high yields. 6 This method is particularly useful in quantitative analysis of fatty acids by gas chromatography. 7 (Figure presented) Both cyclic and acyclic ketones react with TMSCHN2 in the presence of boron trifluoride etherate to give the ring or chain homologated ketones. The steric bulk of the trimethylsilyl group promotes regioselective methylene insertion. 8 (Figure presented) (C) While TMSCHN2 will only react with activated nitriles, its lithium salt, TMSC(Li)N2 reacts smoothly with aromatic, heteroaromatic and aliphatic nitriles to give the corresponding 4-substituted 5-trimethylsilyl-1,2, 3-triazoles. 9 Reaction of TMSC(Li)N2 with α, β-unsaturated nitriles can also afford pyrazoles in some cases. 10 (Figure presented) (D) TMSCHN2 has been employed in asymmetric dipolar cycloadditions with chiral acrylates, to afford optically active Δ 2-pyrazolines. 11 The cycloadditions proceed in high yield with a high degree of diastereoselectivity. This methodology has also been applied to the synthesis of the indolizidine metabolite stellettamide A. 12,13 (Figure presented) (E) TMSCHN2 reacts directly with N-sulfonyl imines to furnish C-silylaziridines in good yields and high cis-stereoselectivities. 14, 15 The resulting products undergo substitution of the silyl group with high diastereoselectivity and ring opening by nucleophiles with complete regioselectivity. (Figure presented).