Coupling reaction of alkynyliodonium salts with alkynylcopper reagents, a new access to liquid-crystalline 1,3-butadiynes

1,4-Disubstituted 1,3-butadiynes bearing long alkyl and alkoxy chains are seletively prepared by the coupling reaction of alkynyliodonium salts with alkylcopper reagents. The length of the alkyl chains both in the alkynyliodonium salts and in the copper reagents is not the significant factor of the coupling reaction and the coupling reaction affords unsymmetrical 1,4-disubstituted 1,3-butadiynes bearing long alkyl chains in good yields. The 1,3-butadiynes prepared in the present study exhibit mesogenic properties.