1,4-Silatropy of S-α-Silylbenzyl Thioesters:  A Convenient Route to Silyl Enol and Dienol Ethers Accompanied by C−C Bond Formation via Thiocarbonyl Ylides

Abstract

A novel convenient method for the generation of thiocarbonyl ylides from readily accessible starting materials and the first synthetic application of in situ generated ylides in the synthesis of silyl enol and dienol ethers, accompanied by C-C bond formation, is described. Under completely neutral conditions without any catalyst or additive, thermal reactions of S-alpha-silylbenzyl thioesters in sealed tubes at 180 degrees C provided silyl enol and dienol ethers in good to excellent yields with high stereoselectivities. This procedure consists of a multistep reaction in a one-pot process, i.e., 1,4-silatropy of S-alpha-silylbenzyl thioesters to give thiocarbonyl ylides, 1,3-electrocyclization of the ylides to give thiiranes, and the extrusion of sulfur from thiiranes to give silyl enol and dienol ethers.

Photoinduced Multicomponent Synthesis of α-Silyloxy Acrylamides, an Unexplored Class of Silyl Enol Ethers

“…The chemistry of silyl enol ethers is now solid, and their use has grown tremendously over the years as they are valuable intermediates in a wide variety of reactions . Many preparative syntheses have been developed to improve both yield and stereoselectivity; silyl enol ethers can now be prepared from a wide range of starting compounds: not only aldehydes and ketones, but also enones, esters, thioesters, and ketoesters can be conveniently transformed into this class of molecules . Despite great advances in the field, preparation of these compounds from α-ketoamides remains a challenge, especially considering secondary amides bearing an acidic hydrogen.…”

S-Phenyl 4-methoxybenzothioate

“…For background to and applications of thioesters, see : Agapiou & Krische (2003); Choi et al (2003); El-Azab & Abdel-Aziz (2012); Horst et al (2007); Howell et al (2006); Jew et al (2003); Liebeskind & Srogl (2000); McGarvey et al (1986); Ozaki et al (2003); Shah et al (2002); Yang & Drueckhammer (2001). For related structures and the synthesis of similar compounds, see: Barbero et al (2003).…”

“…Recently, the α-β-unsaturated thioester analogs have been successfully applied for asymmetric additions which allow the access to chiral intermediates for the synthesis of more complex compounds. Furthermore, they were used in natural product synthesis and also are acting as biologically relevant substances finding application for in vivo tumor suppression (Agapiou & Krische (2003); Barbero et al, 2003;Choi et al, 2003;Horst et al, 2007;Howell et al, 2006;Jew et al, 2003;Liebeskind & Srogl 2000;McGarvey et al, 1986;Ozaki et al, 2003;Shah et al, 2002;Yang & Drueckhammer, 2001). Owing to these applications of thioesters, the title compound (I) was synthesized.…”

A domino pericyclic route to polysubstituted salicylic acid derivatives: four sequential processes from enynones and ketene silyl acetals

“…We report herein a domino pericyclic process en route to poly-substituted salicylic acid derivatives (Scheme 1). The [2+2] cycloaddition of enynone I to ketene silyl acetal (KSA) II (step 1) 2 is a prelude to a three-step domino process, electrocyclic ring opening (step 2), 3 1,5-silatropy (step 3), 4 and 6p-electrocyclization (step 4), 5 allowing access to salicylate VI.…”