N-Sulfonyl acetylketenimine as a highly reactive intermediate for the synthesis of N-sulfonyl amidines

Abstract

A highly reactive intermediate N-sulfonyl acetylketenimine was generated from a 3-butyn-2-one participating CuAAC/ring-opening method. Its high reactivity due to bearing two EWGs allowed us to offer the first example of a reaction between ketenimine and amide to synthesize N-sulfonyl amidines efficiently.

Ynones in Reflex‐Michael Addition, CuAAC, and Cycloaddition, as Well as their Use as Nucleophilic Enols, Electrophilic Ketones, and Allenic Precursors

“…Terminal ynones showed higher reactivity than terminal aryl (or alkyl) alkynes in the CuAAC. [13a], [13b] In 2018, the Hu group[13a] described a novel 3‐butyn‐2‐one‐participated synthesis of N ‐sulfonyl amidines 22.3 and ketenes via the CuAAC/ring‐opening with RSO 2 N 3 (Eq. 22‐1).…”

“…In 2019, the Hu group[13b] extended the application of active intermediates N ‐sulfonyl acetylketenimines 23.1 to reactions with aryl carboxylic acids (Eq. 23‐1).…”

“…N ‐aroylsulfonamides 23.4 were obtained via a novel Mumm‐type rearrangement 23.3 (Scheme ). As reported by the Piggott group,[13c] terminal ynones have been used in the total synthesis of dihydromonosporascone and monosporascone.…”

Copper-Catalyzed One-Pot Synthesis of N-Sulfonyl Amidines from Sulfonyl Hydrazine, Terminal Alkynes and Sulfonyl Azides

“…Classical types of reactions have focused on the preparation of N -sulfonyl amidines involved in the reaction of cyclic thioamides and thioacetamide derivatives with sulfonyl azides [ 14 , 16 , 17 , 18 ], the phosphite-mediated Beckmann-like coupling of oximes and p -toluenesulfonyl azide [ 19 ], sulfonamide derivatives condensation with DMF–DMA [ 20 ], the sulfonamide reaction with formamide [ 21 ] and the sulfonyl ynamide rearrangement [ 22 ]. The most efficient method is the Cu-catalyzed multicomponent reaction of terminal alkynes, sulfonyl azides and amines, which has been applied to synthesize numerous oxygen-containing and nitrogen-containing heterocyclic compounds [ 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 ]. The ketenimine intermediate generated by Cu-catalyzed alkynes and sulfonyl azides [ 31 , 32 , 33 ] could take a nucleophilic addition reaction with most amines, as show in Scheme 1 , including aliphatic primary amines [ 34 , 35 , 36 ], aliphatic secondary amines [ 37 , 38 ], aliphatic tertiary amines [ 39 , 40 ], quaternary amine salts [ 41 ], imines [ 27 ], nitrogenous heterocyclic compounds [ 42 , 43 , 44 , 45 ], urea derivatives [ 46 ], oximes [ 47 ], sulfoximines [ 48 ] and enyl amine [ 49 , 50 ].…”

Rapid and efficient synthesis of formamidines in a catalyst-free and solvent-free system

“… 14–16 The fourth method is a three-component reaction, reported previously by our research team, between a sulfonyl azide, a terminal ynone (3-butyn-2-one) and an amide involving the formation of a highly reactive intermediate N -sulfonyl acetylketenimine reacting with the amide in a [2 + 2] cycloaddition followed by a [2 + 2] cycloreversion with the concomitant generation of 4-oxo-3-buren-2-one ( Scheme 1d ). 17 Recently, Wusiman and colleagues proposed a straightforward one-pot multicomponent approach, but heating and solvent addition are required. 18 Each of the methods described above has considerable advantages, including mild reaction conditions and high efficiency in the assembly of N -sulfonyl formamidines.…”