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.
容易获得的酰基二硫代磷酸酯不稳定,特别是在加热条件下,可以可逆地异构化为O-硫代酰基单硫代磷酸酯。转变为S-硫代酰基单硫代磷酸酯的过程要慢得多,但可能是不可逆的。由于建立了平衡状态,S-硫代酰基(单)硫代磷酸酯的形成较慢,反应混合物通常既含有硫代酰化剂也含有酰化剂,因此无法用于高效的硫代酰化反应。另一方面,将异构酸酐混合物与过量的二硫代磷酸反应,会导致仅形成S-硫代酰基二硫代磷酸酯。它们似乎是非常优秀的硫代酰化剂:相对稳定,对水和氧气不敏感,因此易于处理。它们在常温下与氮或硫亲核试剂的反应非常迅速,产生相应的硫代酰基衍生物。产品的分离非常简单。由于S-硫代酰基二硫代磷酸酯对氧亲核试剂的反应性较低,因此它们可以用于直接硫代酰化多功能亲核试剂,而不需要保护羟基。使用其他方法不易获得相应的硫代酰基衍生物。