Polylithiumorganic compounds - 23. 1: 3,4-dilithio-1,2-butadienes by addition of lithium metal to 1,4-unsymmetrically substituted butatrienes

Article abstract of DOI:10.1016/0040-4020(96)00235-9

The synthesis of the highly reactive 1,4-unsymmetrically substituted butatrienes 12a-c is described. When employing a strict synthetic protocol, these alkatrienes react with lithium metal to 3,4-dilithio-1,2-butadienes 20a-c as stable intermediates. The structure of 20 is supported by IR and NMR spectroscopic evidence. The same dianionic intermediate can be prepared in one case by double deprotonation of the 1,2-butadiene 19. Upon derivatization, either 3,4-disubstituted 1,2-butadienes 24, 2,3-disubstituted 1,3-butadienes 25, or 1,4-disubstituted 2-butynes 26 are formed, depending on the nature of the electrophile employed. Copyright