An Organocatalytic Process for the Hydrolytic Cleavage of Dithianes Mediated by Imidazolium Ions: No Harsh Agents Required

Abstract

A new, organocatalytic approach to the hydrolytic deprotection of dithianes has been developed involving a low‐toxicity imidazolium‐ion‐based catalyst in an aqueous medium. A complimentary solvent‐free method without added water and involving a sacrificial aldehyde is also reported. The catalyst does not appear to operate by a specific‐acid catalysis mechanism.

Recent Progress on the Mild Deprotection of Dithioketals, Dithioacetals, and Oxathiolanes

“…An organocatalytic system for the cleavage of dithianes and dithiolanes of aldehydes and ketones was proposed by Connon by using different classes of imidazolinium‐ions‐based ILs (Scheme 27). [53] This study found imidazolinium salt 7 to be the best catalyst in this study for deprotecting various dithiane derivatives. Substituted dithianes were thus deprotected in acceptable yields using 10 mol% of 7 in a dioxane‐H 2 O mixture at 100 °C.…”

Acid‐Catalyzed Activation and Condensation of the =C5H Bond of Furfural on Aldehydes, an Entry Point to Biobased Monomers

“…One should note that Connon et al . have documented a catalytic procedure for the deprotection of the dithiol moiety, opening the possibility to potentially recycle and re‐use 1,2‐ethanethiol [51] …”

“…The recycling of the 1,2‐ethanethiol is thus mandatory to lower the price of 3 to an acceptable level for polymer applications. As above mentioned, following the catalytic method outlined by Connon et al ., [51] 1,2‐ethanethiol can be regenerated, thus offering a potential way to recycle it (variant 2). Using an average deprotection yield reported in their study (78 mol %), the estimated cost for compound 3 significantly decreases to 4.2 $/kg using variant 2.…”

PhIO-Mediated oxidative dethioacetalization/dethioketalization under water-free conditions

“…For a representative example, the lithium anions of aldehyde 1,3-dithianes could be utilized as nucleophiles for the formation of new C-C bonds, providing a practical umpolung approach for further alkylating of the substrates. [5][6][7] Cyclic thioacetals and thioketals, such as 1,3-dithiolanes and 1,3dithianes, have been commonly used in various organic transformations due to their easy preparation and high stability against the acidic/basic conditions. 8 However, regeneration of the parent carbonyl species via removal of the thio moiety is often not an easy task.…”