Thioketals

Thioketals

General structure of thioketals (more precisely: dithioketals). The following applies: R 1 to R 4 are organyl residues (alkyl residues, aryl residues, arylalkyl residues, etc.), but not a hydrogen atom. [For R 3 and / or R 4 hydrogen: thioacetal (more precisely: dithioacetal)].

General structure of the monothioketals. The following applies: R 1 to R 3 are organyl residues (alkyl residues, aryl residues, arylalkyl residues, etc.), but not a hydrogen atom. (For R 3 and / or R 4 hydrogen: monothioacetal).

In chemistry, a thioketal (more precisely: dithioketal) is a ketal in which both acetal oxygen atoms have been replaced by sulfur atoms. With the monothioketals only one of the two acetalic oxygen atoms of a ketal is replaced by a sulfur atom.

Today thioketals are mostly subsumed under the term thioacetals , although the former are derived from ketones and not from aldehydes .

synthesis

To synthesize a thioketal, a ketone is acid-catalyzed with a monohydric or dihydric thioalcohol or reacted in the presence of zinc chloride with elimination of water. Alternatively, in the Corey-Seebach reaction, thioacetals are first deprotonated with a base. The anion formed in this way delivers the corresponding thioketal in the subsequent reaction with an alkyl halide:

Synthesis of a thioketal by the Corey-Seebach reaction.

use

The oxidation of thioketals e.g. B. with potassium permanganate disulfone provides:

The reduction of thioketals with Raney nickel results in alkanes .

Individual evidence

1. ^ ^{A b} Brockhaus ABC Chemie, VEB FA Brockhaus Verlag Leipzig 1965, page 1410.
2. ^ RL Shriner, JM Cross, Elmer H. Dobratz: Dialkyl bis (carbethoxymethanesulfonyl) methanes . In: Journal of the American Chemical Society . tape 61 , no. 8 , 1939, pp. 2001-2003 , doi : 10.1021 / ja01877a015 .