352559-92-3Relevant academic research and scientific papers
Spiro-fused cyclopentadienes and novel pyridinium carbonyltungstates from (1-alkynyl)carbene tungsten complexes and exo-methylene n-heterocycles. Competition between 1,4-addition, 1,2-addition, and metathesis
G?ttker-Schnetmann,Aumann, Rudolf,Kataeva, Olga,Holst, Christiane,Fr?hlich, Roland
, p. 2889 - 2904 (2008/10/08)
Reaction of (1-alkynyl)carbene tungsten complexes 1a-c with different exo-methylene N-heterocycles was found to yield 1,4- and 1,2-adducts as well as metathesis products in ratios depending on structural details. 2-Methyleneindoline 2a gave conjugated metallahexatrienes 4a,c and cross-conjugated metallahexatrienes 3a,c by 1,4-addition and metathesis, respectively. Cross-conjugated metallahexatrienes were shown to be thermally transformed in conjugated metallahexatrienes by a skeletal rearrangement. 2-Propenylideneindolines 2b-d afforded cross-conjugated metallaoctatetraenes 8 and 9 resulting from metathesis of the exo-propenylidene moiety at the 1,2- and the 3,4-double bond position, respectively. 2-Methylene-1,2-dihydropyridines 12a,b and 4-methylene-1,4-dihydropyridines 13c-e yielded conjugated metallaoctatetraenes 14 and 15 in each case by 4-addition, which underwent a π-cyclization to spiro compounds 16 and 17, respectively. 4-Methylene-1,4-dihydropyridines 13f,g afforded no 4-addition products but novel pyridinium carbonylmetalates 18 by 2-addition.
