Rare-earth silylamide-catalyzed selective dimerization of terminal alkynes and subsequent hydrophosphination in one pot.
[reaction: see text] Rare-earth silylamides, Ln[N(SiMe3)2]3 (Ln = Y, La, Sm), catalyzed regio- and stereoselective dimerization of terminal alkynes in the presence of amine additives to give conjugated enynes in high yields. The additives played a crucial role to depress the oligomerization and to control the regio- and stereochemistry of the dimerization. Thus, the selectivity for (Z)-head-to-head enynes was increased in the order of tertiary < secondary < primary amine additives. On the other hand, the reversed order was observed for the formation of head-to-tail dimers. When alpha,omega-diynes were subjected to the dimerization, very novel cyclic bisenyne compounds were given through double-dimerization in satisfactory yields. In addition, an application of the system allowed subsequent hydrophosphination of the enynes generated in situ with diphenylphosphine, giving rise to 1-phosphinyl-1,3-dienes as the sole products in excellent yields after oxidative workup.
Komeyama
Kimihiro
K
Department of Chemistry and Chemical Engineering, Graduate School of Engineering, Hiroshima University, Kagamiyama, Higashi-Hiroshima 739-8527, Japan. kkome@hiroshima-u.ac.jp
Kawabata
Tomonori
T
Takehira
Katsuomi
K
Takaki
Ken
K
D000480:Alkynes / Q000737:chemistry*; D002070:Butadienes / Q000138:chemical synthesis*; D002384:Catalysis; D019281:Dimerization; D008674:Metals, Rare Earth / Q000737:chemistry*; D010720:Phosphines / Q000737:chemistry; D014297:Trimethylsilyl Compounds
D000480:Alkynes; D002070:Butadienes; D008674:Metals, Rare Earth; D010720:Phosphines; D014297:Trimethylsilyl Compounds