In
organosulfur chemistry, a thioketal is the
sulfur
Sulfur ( American spelling and the preferred IUPAC name) or sulphur ( Commonwealth spelling) is a chemical element; it has symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms ...
analogue of a
ketal
In organic chemistry, an acetal is a functional group with the connectivity . Here, the R groups can be organic fragments (a carbon atom, with arbitrary other atoms attached to that) or hydrogen, while the R' groups must be organic fragments n ...
(), with one of the
oxygen
Oxygen is a chemical element; it has chemical symbol, symbol O and atomic number 8. It is a member of the chalcogen group (periodic table), group in the periodic table, a highly reactivity (chemistry), reactive nonmetal (chemistry), non ...
replaced by
sulfur
Sulfur ( American spelling and the preferred IUPAC name) or sulphur ( Commonwealth spelling) is a chemical element; it has symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms ...
(as implied by the ''
thio-'' prefix), giving the structure . A dithioketal has ''both'' oxygens replaced by sulfur ().
Thioketals can be obtained by reacting
ketones
In organic chemistry, a ketone is an organic compound with the structure , where R and R' can be a variety of carbon-containing substituents. Ketones contain a carbonyl group (a carbon-oxygen double bond C=O). The simplest ketone is acetone ( ...
() or
aldehydes
In organic chemistry, an aldehyde () (lat. ''al''cohol ''dehyd''rogenatum, dehydrogenated alcohol) is an organic compound containing a functional group with the structure . The functional group itself (without the "R" side chain) can be referred ...
() with
thiols
In organic chemistry, a thiol (; ), or thiol derivative, is any organosulfur compound of the form , where R represents an alkyl or other organic substituent. The functional group itself is referred to as either a thiol group or a sulfhydryl grou ...
().
An oxidative
cleavage
Cleavage may refer to:
Science
* Cleavage (crystal), the way in which a crystal or mineral tends to split
* Cleavage (embryo), the division of cells in an early embryo
* Cleavage (geology), foliation of rock perpendicular to stress, a result of ...
mechanism has been proposed for dithioketals, which involves thioether oxidation, the formation of thionoiums, and
hydrolysis
Hydrolysis (; ) is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution reaction, substitution, elimination reaction, elimination, and solvation reactions in which water ...
, resulting in the formation of aldehyde and ketone products.
Thioketal
moieties are found to be responsive to
reactive oxygen species
In chemistry and biology, reactive oxygen species (ROS) are highly Reactivity (chemistry), reactive chemicals formed from diatomic oxygen (), water, and hydrogen peroxide. Some prominent ROS are hydroperoxide (H2O2), superoxide (O2−), hydroxyl ...
(ROS).
In the presence of ROS, thioketals can be selectively cleaved.
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.
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
Raney nickel , also called spongy nickel, is a fine-grained solid composed mostly of nickel derived from a nickel–aluminium alloy. Several grades are known, of which most are gray solids. Some are pyrophoric, but most are used as air-stable s ...
in a reaction known as the
Mozingo reduction.
See also
*
Thioacetal
References
{{orgchem-stub
Functional groups
Organosulfur compounds