89861-45-0Relevant articles and documents
Lawesson's reagent for direct thionation of hydroxamic acids: Substituent effects on LR reactivity
Przychodzen, Witold
, p. 676 - 684 (2007/10/03)
To explore the generality and scope of direct thionation of hydroxamic acids (HAs), the reaction of various structurally diverse HAs with Lawesson's reagent was investigated. The yield of thiohydroxamic acid (THAs) is poor when HAs possess bulky acyl and/or N-substituents, acidic α-hydrogen atoms, or an N-phenyl ring. THAs yields were correlated with Brown sigma parameter. The relative rates of two subsequent processes kT2 and kR2 were also measured. Correlation was also found for methine proton chemical shifts of N-isopropyl benzothiohydroxamic acids.
Synthesis of S-thioacyl dithiophosphates, efficient and chemoselective thioacylating agents
Doszczak, Leszek,Rachon, Janusz
, p. 1271 - 1279 (2007/10/03)
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.
New, efficient and chemoselective method of thioacylation, starting from carboxylic acids
Doszczak,Rachon
, p. 2093 - 2094 (2007/10/03)
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.
