Rongalite as a Versatile Reagent in Organic Synthesis^†

Abstract

Comprehensive SummaryThis review provides a comprehensive summary of progress to date in the utilization of rongalite as a versatile reagent in organic synthesis, with a focus on recent research. The contents have been organized according to the functions exhibited by rongalite. Reaction mechanisms are provided, demonstrating the multifaceted roles of this compound in various transformations, including as a sulfone, C1 or masked proton source and as a single electron donor or reducing agent.This article is protected by copyright. All rights reserved.

Photocatalytic Synthesis and Functionalization of Sulfones, Sulfonamides and Sulfoximines

“…[19,20] The latter is one of the reasons why SO 2 has been used as the most direct sulfonyl source in radical chemistry. Taking into account that SO 2 is a gas at room temperature, different SO 2 surrogates can be found in the literature, being DABCO • (SO 2 ) 2 , [21] rongalite [22,23] and K 2 S 2 O 5 (or Na 2 S 2 O 5 ) [24] the most used ones. The high tendency of these surrogates to act as radical traps, leading to the formation of the corresponding sulfonyl radicals has been exploited in the literature for the last decade in numerous examples.…”

Rongalite as a C1 Source: Sulfonylmethylation of Indoles with Aryl/Alkyl Hydrazides and Sulfinates

“…The synthesis of rongalite (sodium hydroxymethanesulfinate dihydrate) dates back to 1905, and its chemical structure was elucidated on 1962 . Rongalite is an inexpensive commodity chemical that has found extensive use in the rubber, dye, and veterinary industries . Rongalite participates in a large array of synthetic transformations, the most popular being as reductants and a source of sulfoxylate (SO2 2– ) equivalent in sulfonylation reactions .…”

“…Rongalite is an inexpensive commodity chemical that has found extensive use in the rubber, dye, and veterinary industries . Rongalite participates in a large array of synthetic transformations, the most popular being as reductants and a source of sulfoxylate (SO2 2– ) equivalent in sulfonylation reactions . Recently, our group has developed a method for incorporating a sulfone group (from rongalite) for 1,6-conjugate reactions with para -quinone methides and alkyl/aryl halides .…”

Palladium-catalyzed domino cyclization/direct functionalization involving the insertion of SO2

“…Traditional approaches for the synthesis of sulfonyl compounds consist of alkylation of sulfinate salts 8 or oxidation of sulfides with strong oxidants, 9 which need to use poorly accessible organosulfur compounds as starting materials and have several drawbacks, including limited applicability, harsh conditions, and complicated operations. In response to these limitations, strenuous efforts have been made for the preparation of sulfonyl compounds through radical or catalytic SO 2 insertion reactions, 10 in which DABSO (DABCO·2SO 2 ), 11 metabisulfite (Na 2 S 2 O 5 /K 2 S 2 O 5 ), 12 rongalite reagent, 13 and SOgen 14 are usually used as SO 2 surrogates. Among them, transition metal-catalyzed SO 2 insertion reactions generally contain two steps involving sulfinates as key intermediates (Scheme 1a).…”