K₂CO₃-Catalyzed Rapid Conversion of N-Sulfonylhydrazones to Sulfinates

Abstract

N -Sulfonylhydrazones derived from alkyl, aryl, and heteroaryl aldehydes and ketones undergo rapid conversion into the corresponding sulfinates when heated with 10 mol % K 2 CO 3 in N , N ′-dimethylethylene urea (DMEU) at elevated temperature. The reaction conditions are amenable to several functional groups and suitable for gram-scale synthesis. Under these base-catalyzed conditions, N -tosylhydrazones derived from O -allylated and O -propargylated 2-hydroxyarylaldehydes do not undergo the well-established intramolecular [3 + 2]-cycloaddition reactions and generate corresponding sulfinates in good yields. The base-catalyzed transformation proceeds via crucial rapid intermolecular protonation of the diazo intermediate 11 to generate diazonium ion 12 , which upon nucleophilic displacement by the sulfonyl ion 10 provides the desired sulfinate selectively.

Synthesis of Multifluoromethylatedγ‐Sultines by a Photoinduced Radical Addition–Polar Cyclization

“…The sulfinate species 62 bears a negative charge on the O-atom in a polar aprotic solvent and is favored over the negatively charged Scenter in 61, and is a crucial for the success of the catalytic conditions. [14] Intermediate 61 either reverts to 59 by SET oxidation or derives from 64 by SO 2 addition. Finally, 62 undergoes a polar 5-exo-tet cyclization to yield P. In the meanwhile, two competitive pathways involving cyclopropanation [18] and protonation [20] of carbanion intermediate 64 from SET between 59 and PC *À are also possible, although not observed in this reaction, indicating the distinct reactivity of this cascade cyclization reaction.…”

“…The choice of the solvent was crucial, wherein MeCN was optimal, and DMF and DMSO were also suitable. DCE and dioxane were inferior (entries 4–7), and attributed to the low dissolution capacity of CF 3 SO 2 Na and the negatively charged O‐center of the ambient sulfonyl anion as the favored nucleophile, over the negatively charged sulfur center, in polar aprotic solvent [14] . Remarkably, the catalyst loading was found to have a slight effect on the yield, with 1 mol% 4CzIPN providing 87 % yield of 3 (entry 8).…”

“…Then, the pivotal incorporation of SO 2 with 59 provides the sulfonyl radical 60 , which undergoes SET with the reduced state of the photocatalyst ( PC⋅ − , E 1/2 [PC/PC⋅ − ]=−1.21 V vs. SCE in MeCN for 4CzIPN) to give sulfonyl anion 61 . The sulfinate species 62 bears a negative charge on the O‐atom in a polar aprotic solvent and is favored over the negatively charged S‐center in 61 , and is a crucial for the success of the catalytic conditions [14] . Intermediate 61 either reverts to 59 by SET oxidation or derives from 64 by SO 2 addition.…”

“…DCE and dioxane were inferior (entries 4-7), and attributed to the low dissolution capacity of CF 3 SO 2 Na and the negatively charged O-center of the ambient sulfonyl anion as the favored nucleophile, over the negatively charged sulfur center, in polar aprotic solvent. [14] Remarkably, the catalyst loading was found to have a slight effect on the yield, with 1 mol% 4CzIPN providing 87 % yield of 3 (entry 8). An even further lowering of the catalyst loading to 0.1 mol% still worked well (entry 9).…”

Pd-Catalyzed Rearrangement Reaction of N-Tosylhydrazones Bearing Allyl Ethers Into Trans-Olefin-Substituted Sulfonylhydrazones

“…QuinShimizu’s group developed a method for the oxidation of N -sulfonyl hydrazide catalyzed by lead tetraacetate ( Scheme 1A ) ( Shimizu et al, 1980 ). Subsequently, Ashok et al established a new scheme for the synthesis of sulfinates ( Scheme 1B ) through the K 2 CO 3 -catalyzed rapid conversion of N -sulfonyl hydrazide ( Korawat and Basak, 2020 ). Hossain et al reported a synthetic route to 1,3-disubstituted allenes through the CuI-catalyzed cross-coupling of N -tosylhydrazones with terminal alkynes ( Scheme 1C ) ( Hossain et al, 2013 ).…”