2-Pyridyl triflates synthesis

Table 4 Synthesis of substituted 2-pyridones 60 and 2-pyridyl triflates 62...

The triflate leaving group was introduced to coupling reactions as an alterative to halogens. They are particularly useful when there is no simple way to prepare the required halide partner. Aryl triflates can be prepared from phenols and pyridyl triflates can be prepared from pyridones. This transformation is usually achieved using triflic anhydride and an amine base. The coupling of a triflate 2.191, derived from quinolone 2.190, with stannane 2.192 was used in a short synthesis of dubamine 2.193 (Scheme 2.66). 

The synthesis of platinum polyynes with heteroaromatic organic spacer groups has also been readily accomplished, for example, species 188 with skeletal pyridyl units that make use of the dehydrohalogenation method (Scheme 16(a)) or an McsSnCl elimination procedure analogous to that in Equation (64) (Scheme 17)." The resultant polymers could be quaternized at nitrogen with methyl iodide and triflate. Materials such as 189 with a bithiazole spacer have also been prepared by the dehydrohalogenation method. 

Abiraterone acetate 117 is an androgen biosynthesis inhibitor, which was developed by the Institute of Cancer Research in the UK and further developed by Janssen for the oral treatment of patients with metastatic castration-resistant prostate cancer [75]. Its synthesis is relatively easy through a Suzuki coupling between the 17-enol triflate derived from the 3-acetate of dehydro-epiandrosterone (115) and 3-pyridyl-diethylborane (116) (Scheme 27) [76]. The reaction is catalysed by PdCl2(PPh3)2 and proceeds in good yield (84%). A similar Suzuki-based route in which the ketone starting material was converted into an alkenyliodide has also been published [77]. 

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