the (Z)-isomer. The latter compound was also formed from a two-step reaction; Sonogashira coupling with O-silylated alkyne followed by deprotection and subsequent 5-exo cyclization. Sonogashira coupling between 6-halopurines and 2-propynylphenol gave only the alkyne coupling product and no cyclization took place. However, the Sonogashira product was unexpectedly rearranged to 6-(3-phenoxypropa-1,2-dienyl)purines
研究了6-[((2-羟基苯基)
乙炔基]
嘌呤,6-[((2-羟基甲基苯基)
乙炔基]
嘌呤和6-[((2-羟基苯基)
丙炔基-1-基]
嘌呤)的环化反应。通过一锅Sonogashira偶联–
6-碘嘌呤和
2-乙炔基苯酚之间的环化反应,可以轻松获得6-(2-
苯并呋喃基)
嘌呤。当与邻-(羟甲基)
乙炔基苯进行相同的反应时,形成了6- [
异苯并呋喃-1(3H)-亚甲基甲基]
嘌呤,主要为(E)-异构体。(E)-化合物的酸催化异构化得到(Z)-异构体。后者的化合物也是由两步反应形成的。Sonogashira与O-
硅烷化的
炔烃偶联,然后脱保护并随后进行5-外环化。6-卤代
嘌呤和2-
丙炔基
苯酚之间的Sonogashira偶联仅产生
炔烃偶联产物,并且未发生环化。但是,在碱性条件下,Sonogashira产物出乎意料地重排为6-(3-苯氧基丙-1,1,2-二烯基)
嘌呤。理论计算表明,
丙二烯比其
炔烃异构体更稳定。