First catalyst-free CO₂trapping ofN-acyliminium ions under ambient conditions: sustainable multicomponent synthesis of thia- and oxazolidinyl carbamates

Abstract

The first trapping of N-acyliminium ions by in situ generated carbaminic acid (product of carbon dioxide (CO2) and amine) is reported. This catalyst-free reaction provides a convenient and feasible approach to prepare N-acyl thia- and oxazolidinyl carbamates with good functional-group compatibility and high efficiency under green conditions. Furthermore, the multicomponent method features a broad substrate scope, facile product diversification, smooth scale-up and notable potential for polymer applications.

Catalytic Approaches to Multicomponent Reactions: A Critical Review and Perspectives on the Roles of Catalysis

“…Isocyanide-based MCRs are sometimes performed in the absence of catalysts [ 62 ], but their catalytic versions proved to have many advantages. Some catalyst-free MCRs have been induced by alternative conditions, such as light-promoted reactions [ 63 ], microwave irradiation [ 64 ] and a few others [ 65 , 66 , 67 , 68 ], but catalysis effects rather than these conditions are of interest in the current article. Some MCRs have been labeled “catalyst-free”, but they have also been elegantly questioned [ 69 ], whereas other so-called “catalyst-free” MCRs could not be reproduced at all.…”

Transition Metal‐Free Synthesis of Carbamates Using CO2 as the Carbon Source

“…In the same year, Martens and co-workers reported a catalyst-free reaction of carbon dioxide and N-acyliminium ions under ambient conditions to form complex thia-and oxazolidinyl carbamates. [33] They utilized carbon dioxide under balloon pressure in a four-component reaction strategy utilizing acetyl chloride as the substrate. The reaction had to be performed in two steps and needed cooling by ice bath.…”

Stereospecific Synthesis of cis/trans-dicarbamates

“…On the other hand, isocyanates such as 4-methyl-benzenesulfonyl isocyanate (p-TsNCO) and phenyl isocyanate (PhNCO) are frequently used in the preparation of aminocyclitols and are also widely used in the preservation of alcohols (Huang & Yan, 2017;Kelebekli, 2020;Seo & Chung, 2017;Trost & Kalnmals, 2020). In addition, some drugs containing halogen atoms as well as carbamate function are widely reported in the literature (Scattolin et al, 2019), such as capravirine 1 (Li et al, 2012), 1benzoxazin-4-yl]methyl-(4-fluorophenyl)carbamate 2 (Mizutani et al, 2009) that is antibacterial drug, Rivastigmine 3 for Alzheimer's disease (Franz et al, 2018), monocarbamate 4 (Kelebekli, 2022) (Figure 1).…”