Yadav Navin, Payra Soumen, Tamuly Parag, Narasimha Moorthy Jarugu
Department of Chemistry, Indian Institute of Technology, Kanpur 208016, India.
School of Chemistry, Indian Institute of Science Education and Research, Thiruvananthapuram 695551, India.
Org Biomol Chem. 2023 Oct 11;21(39):7994-8002. doi: 10.1039/d3ob01162c.
The synthesis of β-hydroxysulfones selectively in preference to β-ketosulfones by dye-sensitized photocatalysis is demonstrated by employing inexpensive and readily available olefins and sulfonyl hydrazides/-hydroxy sulfonamides in the presence of oxygen. The facile hydroxysulfonylation reaction, which involves the use of rose bengal (RB) as a photocatalyst and dioxygen as an oxidant, permits access selectively to secondary and tertiary β-hydroxysulfones in good to excellent isolated yields at rt and is compatible with aryl, heteroaryl and alkyl sulfonyl hydrazides. Mechanistically, sulfonyl radicals are generated by a cascade of redox reactions, set off by the photocatalyst RB, between sulfonyl hydrazide and dioxygen. Attack of the sulfonyl radicals on olefins followed by oxygenation of the radical intermediates leads to hydroxysulfonylation products selectively without the requirement of a metal catalyst/additive/reductant/base, conforming to the tenets of sustainable chemistry. It is shown that the formations of β-hydroxysulfones and β-ketosulfones proceed concurrently through two different routes and that the outcome is crucially dependent on oxygen concentration with the former being formed predominantly under an oxygen atmosphere, a feature that is heretofore unprecedented to the best of our knowledge.
通过使用廉价且易于获得的烯烃和磺酰肼/β-羟基磺酰胺，在氧气存在下，通过染料敏化光催化选择性地合成β-羟基砜而不是β-酮砜得以证明。这种简便的羟基砜化反应，使用玫瑰红（RB）作为光催化剂，氧气作为氧化剂，在室温下能够以良好至优异的分离产率选择性地获得仲和叔β-羟基砜，并且与芳基、杂芳基和烷基磺酰肼兼容。从机理上讲，磺酰基自由基是由光催化剂RB引发的磺酰肼与氧气之间的一系列氧化还原反应产生的。磺酰基自由基对烯烃的攻击，随后自由基中间体的氧化，导致选择性地生成羟基砜化产物，而无需金属催化剂/添加剂/还原剂/碱，符合可持续化学的原则。结果表明，β-羟基砜和β-酮砜的形成通过两条不同的途径同时进行，并且结果关键取决于氧气浓度，前者在氧气气氛下主要形成，据我们所知，这一特征是前所未有的。
