Thioketal

In organosulfur chemistry, a thioketal is the sulfur analogue of a ketal (R2C(OR)2), with one of the oxygen replaced by sulfur (as implied by the thio- prefix), giving the structure R2C(SR)OR. A dithioketal has both oxygens replaced by sulfur (R2C(SR)2).

General chemical structure of a dithioketal

Thioketals can be obtained by reacting ketones (>C=O) or aldehydes (−CH=O) with thiols (−SH).

An oxidative cleavage mechanism has been proposed for dithioketals, which involves thioether oxidation, the formation of thionoiums, and hydrolysis, resulting in the formation of aldehyde and ketone products.[1]

Thioketal moieties are found to be responsive to reactive oxygen species (ROS).[1] In the presence of ROS, thioketals can be selectively cleaved.[2] ROS successfully cleave heterobifunctional thioketal linkers, which have been found to have therapeutic potential, as they can produce ROS-responsive agents with two different functionalities.[2]

Ketones can be reduced at neutral pH via conversion to thioketals; the thioketal prepared from the ketone can be easily reduced by catalytic hydrogenation using Raney nickel in a reaction known as the Mozingo reduction.

See also

References
  1. Liu, Bin; Thayumanavan, S. (December 2020). "Mechanistic Investigation on Oxidative Degradation of ROS-Responsive Thioacetal/Thioketal Moieties and Their Implications". Cell Reports Physical Science. 1 (12): 100271. Bibcode:2020CRPS....100271L. doi:10.1016/j.xcrp.2020.100271. ISSN 2666-3864.
  2. Ling, Xiaoxi; Zhang, Shaojuan; Shao, Pin; Wang, Pengcheng; Ma, Xiaochao; Bai, Mingfeng (September 2015). "Synthesis of a reactive oxygen species responsive heterobifunctional thioketal linker". Tetrahedron Letters. 56 (37): 5242–5244. doi:10.1016/j.tetlet.2015.07.059. ISSN 0040-4039. PMC 4545510. PMID 26309336.
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