Metal-Free Oxidative Spirocyclization of Alkynes with Sulfonylhydrazides Leading to 3-Sulfonated Azaspiro[4,5]trienones

Abstract

A novel and direct oxidative spirocyclization of arylpropiolamides with sulfonylhydrazides leading to 3-sulfonated azaspiro[4,5]trienones has been developed under metal-free conditions. The reaction is performed in a tandem manner constituted by the sequential sulfonylation of alkynes, ipso-carbocyclization, dearomatization, hydration, and oxidation processes, providing a convenient and efficient approach to various sulfonated azaspiro[4,5] trienones of biological importance.

Copper(i)-mediated synthesis of β-hydroxysulfones from styrenes and sulfonylhydrazides: an electrochemical mechanistic study

“…On the basis of the obtained experimental data and previous studies of reactions proceeding through the generation of Scentered radicals from sulfonylhydrazides, [33][34][35] we proposed the pathway of the oxysulfonylation process (Scheme 4). Cu(I) ions are oxidized to Cu(II) [36][37][38][39][40] in the presence of oxygen, as conrmed by numerous kinetic studies of this process.…”

The Persistent Radical Effect in Organic Synthesis

“…[60,61] Another beautiful sequence taking advantage of the PRE with peroxyl radicals as in situ generated scavengers is shown in Figure 14 a. Thee sters and amides 44 derived from propiolic acid derivatives and anilines or phenols were used as radical acceptors.I nt he first step,at ransient radical generated by ar edox reaction adds regioselectively to the CÀCt riple bond of 44 to give av inyl radical 45.I ts ipso cyclization onto the arene of the aniline or phenol moiety leads to cyclohexadienyl radical 46,w hich is trapped by tertbutylperoxyl to give peroxide 47,which can undergo aK ornblum-DeLaMare rearrangement [62] to finally provide ketone 48.T his sequence was successfully conducted with various radicals RC using different radical precursors.A lkyl radicals derived from ethers, [63] ketones, [64] or alkanes, [65] acyl radicals from aldehydes, [66] CF 3 radicals from the Langlois reagent, [67] SCF 3 radicals from AgSCF 3 , [68] silyl radicals from silanes, [69] and sulfonyl radicals from sulfonylhydrazides engage in this spirocyclization cascade. [70] Recently,t he groups of Wu and Zhong presented an oxidative cyclization of ethylene-bridged aminoindoles 48 to afford peroxypyrroloindolines 49 with t-BuOOH as the oxidant in combination with TBAI ( Figure 14 b). [71] The long-lived peroxyl radical is first used for the generation of radical 50 by HATf rom the indole N À Hg roup.T his radical then undergoes selective radical-radical cross-coupling with a tert-butylperoxyl radical to give indolenine 51.A minal formation (52)a nd oxidation eventually provide 49.…”

“…a) Radical spirocyclization with the tert-butylperoxyl radical as atrapping reagent. [63][64][65][66][67][68][69][70] b) Oxidative indole functionalization to access peroxypyrroloindolenines 49. [71] Figure 15.…”

Der “Persistent Radical Effect” in der organischen Chemie

“…Diese Sequenz wurde mit einer Vielzahl verschiedener Radikale RC durchgeführt. In dieser spiro-Cyclisierung wurden Alkyl-Radikale von Ethern, [63] Ketonen [64] bzw.A lkanen, [65] Acyl-Radikale von Aldehyden, [66] CF 3 -Radikale vom Langlois-Reagenz, [67] SCF 3 -Radikale vom AgSCF 3 , [68] Silyl-Radikale von Silanen [69] und Sulfonyl-Radikale von Sulfonylhydraziden [70] eingesetzt.…”