149. Dithiols. Part XII. The alkaline hydrolysis of acetylated hydroxy-thiols: a new reaction for the formation of cyclic sulphides

Abstract

Deacetylation, with dilute aqueous alkali, of either the 0or the S-acetyl derivative of 2-mercaptoethanol leads to the formation of ethylene sulphide and polymeric material. cycZoHexene sulphide is obtained in good yield by deacetylation of the 0or S-acetyl derivative of trans-2-mercaptocycZohexano1 with hot aqueous sodium carbonate ; under more vigorous conditions the sulphide undergoes further reactions. Anomalous results reported earlier in the alkaline deacetylation of triacetyl 2 : 3-dimercaptopropanol (triacetyl BAL) have been fully explained ; the initial product is 3-acetylthiopropylene sulphide, which under mild conditions can be isolated (yield SO%), but otherwise reacts further to give 3-hydroxy-2 : 2' : 3'-trimercaptodipropyl sulphide and more complex products. 3-Acetylthiopropylene sulphide is also formed from the di-S-acetyl derivative of 2 : 3-dimercaptopropanol, whilst 2 : 3-dimercaptopropyl acetate gives 3-mercaptopropylene sulphide. The 0and di-S-acetyl derivatives of 3 : 4-dimercaptobutanol give 3-mercaptothiophan, the ring structure of which is proved by partial desulphurisation to thiophan. Cyclisation does not occur on alkaline deacetylation of the 0or the S-acetyl derivative of 2-hydroxy-2'-mercaptodiethyl sulphide. The formation of cyclic sulphides occurs through intramolecular elimination of acetic acid, and involves ester fission of the O-alkyl type.

Native Chemical Ligation and Extended Methods: Mechanisms, Catalysis, Scope, and Limitations

“…The base-catalyzed hydrolysis of alkyl esters in water is known to proceed preferably through the nucleophilic addition of hydroxide ion to the ester carbonyl group (Scheme , path a). The fact that a thiol group in the β position of an acetoxy group accelerates alkaline hydrolysis of an ester bond and proceeds in part through the alternative path b has been largely documented in the past. − According to path b, the carboxylate is produced by intramolecular nucleophilic displacement and ethylene sulfide formation. In fact, 70% of 2-mercaptoethyl acetate hydrolyzes in alkaline media through a regular O -ester hydrolysis mechanism (i.e., path a), while the remaining 30% decomposes through path b with production of ethylene sulfide …”

Using Ring Strain to Control 4π-Electrocyclization Reactions: Torquoselectivity in Ring Closing of Medium-Ring Dienes and Ring Opening of Bicyclic Cyclobutenes

“…The solvent was removed in vacuo . The crude mixture was purified by short path distillation at reduced pressure giving 1.391 g (52% yield) of the known clear colorless oil: Bp = 97 °C (13 mmHg); R f = 0.37 (15:1 Hex/EtOAc); 1 H NMR (400 MHz, CDCl 3 , ppm) δ 2.75 (t, J = 7.4 Hz, 4H), 2.50 (td, J = 7.3, 2.5 Hz, 4H), 2.04 (t, J = 2.6 Hz, 2H); 13 C NMR (100 MHz, CDCl 3 , ppm) δ 82.3, 69.4, 30.8, 19.9; IR (neat, ATR, cm –1 ): 3292, 2959, 2923, 2837, 2116, 1431, 1324, 1284, 1225, 643; HRMS (DART): calcd [M + H] + (C 8 H 11 S) 139.05760, found 139.05713.…”

Shifting Native Chemical Ligation into Reverse through N→S Acyl Transfer

“…This explanation, in addition to the known acid- or base-promoted degradation of acetylated β-hydroxy thiols,[ 23 ] also accounts for the poor stability of thioesters derived from β-mercaptoethanol or dithiothreitol.…”