computational investigation on sulfonyl amidine formation from thioamides and sulfonylazides is described. The data support a non-concerted two-step pathway for the coupling reaction and also indicate that dipole moment of thioamide and electrophilicity of sulfonylazide would be significant factors for the reaction efficiency. A simple reactivity prediction of the coupling reaction was demonstrated by preliminary
A new polymer-supported reagent for the conversion of carbonyls to thiocarbonyls has been developed and its use demonstrated on a range of amides. Secondary or tertiary amides are converted cleanly and efficiently through to the corresponding thioamides and primary amides are converted to the corresponding nitriles. The reactions can be facilitated by conventional heating. However, if microwave heating
Thionation with the Reagent Combination of Phosphorus Pentasulfide and Hexamethyldisiloxane
作者:Thomas J. Curphey
DOI:10.1021/jo0256742
日期:2002.9.1
The combination of P4S10 and hexamethyldisiloxane efficiently converts esters, lactones, amides, lactams, and ketones to their corresponding thiono derivatives. In the presence of elemental sulfur, 3-oxoesters are converted to dithiolethiones by this reagent. Yields are comparable to or superior to those obtained with Lawesson's reagent. The method has the advantage that reagent-derived byproducts
New, efficient and chemoselective method of thioacylation, starting from carboxylic acids
作者:Leszek Doszczak、Janusz Rachon
DOI:10.1039/b005911k
日期:——
S-Acylation of dithiophosphoric acids yields mixed
anhydrides 3; they readily isomerize to O-thioacyl 4 and
S-thioacyl monothiophosphates 5, which treated with the excess of
dithiophosphoric acid 2 can be easily converted into thioacyl
dithiophosphates 6, excellent thioacylating reagents.
Synthesis of S-thioacyl dithiophosphates, efficient and chemoselective thioacylating agentsProofs for the reversibility of isomerisation of anhydrides 1 to 2, melting points of amides and thioamides obtained from anhydrides 5–7 and 1H, 13C NMR and IR data of isolated anhydrides 5–7, 17 are available as supplementary data. For direct access, see http://www.rsc.org/suppdata/p1/b2/b201233b/
作者:Leszek Doszczak、Janusz Rachon
DOI:10.1039/b201233b
日期:2002.5.10
Easily available acyl dithiophosphates are not stable and isomerise reversibly to O-thioacyl monothiophosphates, especially when subjected to heating. Much slower but probably irreversible isomerisation to S-thioacyl monothiophosphates occurs. Since equilibrium states are established and S-thioacyl (mono)thiophosphates form slowly, reaction mixtures contain generally both thioacylating and acylating agents, and consequently cannot be used for efficient thioacylation. On the other hand, treatment of a mixture of isomeric anhydrides with an excess of a dithiophosphoric acid leads to exclusive formation of S-thioacyl dithiophosphates. They appear to be excellent thioacylating agents: relatively stable, inert towards water and oxygen and therefore easy to handle. Reactions with nitrogen or sulfur nucleophiles proceed very rapidly under ambient conditions, yielding respective thioacyl derivatives. Isolation of the products is very simple. Due to
the low reactivity of S-thioacyl dithiophosphates towards oxygen nucleophiles they can be used for direct thioacylation of multifunctional nucleophiles with unprotected hydroxy groups. Respective thioacyl derivatives cannot readily be obtained using other methods.