Controllable Activation of β-Alkyl Nitroalkenes: Regioselective Synthesis of Allyl and Vinyl Sulfones

Abstract

The regiospecific radical reactions of β-alkyl nitroalkenes with sulfonyl hydrazides depended to a great extent on the choice of a solvent and catalyst. In the presence of dimethylformamide (DMF), β-alkyl nitroalkenes more likely converted into electron-rich allyl nitro compounds, which reacted with sulfonyl hydrazides to afford allyl sulfones with high regioselectivity. While in acetonitrile (CH3CN), vinyl sulfones were obtained directly via sulfonation of electron-deficient β-alkyl nitroalkenes. The mechanism investigation revealed that the regioselectivity was controlled by the equilibrium of β-alkyl nitroalkenes and allyl nitro compounds.

Advances in Vinyl Sulfone Catalyzed Synthesis: Methods, Mechanisms and Perspectives

“…further explored the oxidation radical reaction catalyzed by hypervalent iodine and achieved control of the reaction site of the substrate molecule by adjusting the catalyst and solvent types (Scheme 15). [65] Unlike the traditional choice of terminal olefins or alkynes as the vinyl source, Wang chose to use β ‐alkyl nitroalkenes for direct sulfonylation with sulfonyl hydrazides for efficient production of vinyl sulfone under mild conditions (yields of approximately 94 %). The particularity of this scheme lies in the modulation of regiospecific radical reactions of β ‐alkyl nitroalkenes with sulfonyl hydrazides by the selection of solvent and catalyst to obtain the desired products selectively and efficiently.…”

Steric-Hindrance-Induced Diastereoselective Radical Nitration of 3-Alkylidene-2-oxindoles Followed by Tosylhydrazine-Mediated Sulfonation

“…Tian et al reported Pd­(OAc) 2 –BINAP-catalyzed oxidative coupling with sulfonyl hydrazides of allylic amines leading to allylic sulfones. Recently, Chen et al developed an oxidative radical reaction of β-alkyl nitroalkenes and sulfonyl hydrazides toward vinylic and allylic sulfones by tuning the solvent and catalytic system (Scheme ). In this context, the installation of the sulfonyl group with the substitution of the nitro group without using any oxidant and transition metal catalyst is an environmentally benign and operationally simple procedure.…”

Regiodivergent sulfonylation of terminal olefins via dearomative rearrangement

“…Couplings of allylic alcohols with sulfinyl chlorides, 21 activated by NBS, 22 or catalyzed by Pd 3,23 have afforded allylsulfone. Similarly, allylic amines using Pd, 24 allenes using Pd, 25 activated alcohols using W 26 or Ir, 27 alkynes with Rh, 28 dienes with Pd, 29 and allyl halides 30 have been reported to produce allylsulfones; whereas, a-sulfonylmethyl styrenes have been mainly prepared by radical reactions 13,[31][32][33][34][35] or using stoichiometric ZnI 2 . 36 Despite progress, we sought to develop a complementary and tunable synthetic approach (regiodivergent sulfonylation) that utilizes inexpensive and readily available starting materials and reagent under transition metal-free conditions.…”

“…Couplings of allylic alcohols with sulfinyl chlorides, 21 activated by NBS, 22 or catalyzed by Pd 3,23 have afforded allylsulfone. Similarly, allylic amines using Pd, 24 allenes using Pd, 25 activated alcohols using W 26 or Ir, 27 alkynes with Rh, 28 dienes with Pd, 29 and allyl halides 30 have been reported to produce allylsulfones; whereas, α-sulfonylmethyl styrenes have been mainly prepared by radical reactions 13,31–35 or using stoichiometric ZnI 2 . 36…”