Prepn. of oxygen contg. heterocyclic(s) e.g. benzofuran - by cyclisation of phosphonium salts with base in liquid phase

摘要

Prepn. of oxygen heterocyclics of formula (I) comprises cyclisation of phosphonium salts (IIe in the liquid phase in the presence of a base. In the formulae, is an aromatic ring esp. benzene, opt. substd. by oxonitro, hydroxy, halo or organic radicals such as those of R1, R3, R10, r10 O-R10CO, R10COO or R10OOC-, D is -CHR3-O- or -O-, R1, R3 are H, lower alkyl, aryl, aralkyl or cycloalkyl and when D is -CHR3-O- then R1 and R3 may be an organic radical, R2 is H or an organic radical (pref. R10, R10O-), R10 is alkyl, alkenyl, alkynyl, aryl, aralkyl, aralkenyl, aralkynyl or cycloaliphatic, R1 is alkyl, aryl or aralkyl, and X- is an anion. (I) are cpds. such as benzofurnas, chromene and isochromenes which have numerous known uses such as vasodilators (e.g. khellinone), spasmolytics, antibacterials (e.g. 2-(p-nitrophenyl)-benzofuran), parasiticides, stimulants, tranquillisers, endocrine active agents, herbicides, phytohormones, photosensitisers (e.g. psoralene, methoxsalene and trioxsalene) and intermediates. The process is partic. useful for the prepn. of benzofurans, providing a general synthesis, which may give improved yields and allow prodn of cpds. inaccessible by known synthetic routes.