Synthesis of Furoxans and Isoxazoles via Divergent [2 + 1 + 1 + 1] Annulations of Sulfoxonium Ylides and ^tBuONO

Abstract

We have presented a simple and new method for the divergent assembly of furoxans and isoxazoles in which the [2 + 1 + 1 + 1] annulation reaction of sulfoxonium ylides is reported for the first time. When the reaction was performed using tBuONO as the nitrogen source without metal catalyst, the desired furoxans were obtained in decent yields with wide substrate scope. Isoxazoles bearing three carbonyl groups were achieved when the reaction was conducted using Cu­(TFA)2 as catalyst.

tert‐Butyl Nitrite (TBN), a Multitasking Reagent in Organic Synthesis

“…When the reaction was performed under a metal‐free condition using NaOAc as the base, two molecules of sulfoxonium ylides and two molecules of TBN were combined in the product, yielding furoxans having a wide substrate scope. While in Cu‐catalyzed reaction, three molecules of sulfoxonium ylides and one molecule of TBN were fused into the product, yielding three carbonyl groups bearing isoxazoles …”

“…While in Cu-catalyzed reaction, three molecules of sulfoxonium ylides and one molecule of TBN weref used into the product, yielding three carbonyl groups bearing isoxazoles. [103] Electrophilic aromatic nitration is one of the most thoroughly studied substitution reactions,w hile the selective nitration of aliphatic CÀHb onds is very challenginga nd remains almost unrecognized. Nitration of aliphatic hydrocarbons requires very high temperature (> 200 8C) due to the inertness of sp 3 CÀH bonds.S uch high temperature can lead to undesired CÀC bond cleavage and multitudes of products along with loss of selectivity in sp 3 CÀHb onds.…”

Metal-Free Chemoselective Reaction of Sulfoxonium Ylides and Thiosulfonates: Diverse Synthesis of 1,4-Diketones, Aryl Sulfursulfoxonium Ylides, and β-Keto Thiosulfones Derivatives

“…Based on the above experimental results and previous reports, , we propose a plausible mechanism in Scheme . First, homolysis of 2a gives sulfone radical I and a phenylthio radical.…”

Annulation of Conjugated Azine-Imine with a Sulfoxonium Ylide in a Noncarbenoid Route to Synthesize Multisubstituted Imidazole-Fused Heterocycles

“…Recently, a divergent [2+1+1+1]-annulation of Bu t ONO with an aroylsulfoxonium ylide as a carbene precursor has been developed, which provides furoxans and isoxazoles. 6 The study of a sulfoxonium ylide as a 1,1′-dipolar one-carbon synthon, avoiding transitionmetal-carbenoid chemistry, is rare in annulation reactions (Scheme 1B) 7 and has not been identified until now for the construction of fused heteroaromatics. In the aspect of a unique feature of ylides, we previously explored nitrilestabilized ammonium ylide as a masked C−CN synthon (Scheme 1C).…”

“…The β-ketosulfoxonium ylide functions as a traceless bifunctional directing motif in arene C–H functionalization and postannulation reactions. , All of these transformations involve transition-metal-carbenoid chemistry. Recently, a divergent [2+1+1+1]-annulation of Bu t ONO with an aroylsulfoxonium ylide as a carbene precursor has been developed, which provides furoxans and isoxazoles . The study of a sulfoxonium ylide as a 1,1′-dipolar one-carbon synthon, avoiding transition-metal-carbenoid chemistry, is rare in annulation reactions (Scheme B) and has not been identified until now for the construction of fused heteroaromatics.…”