71319-67-0Relevant articles and documents
C(sp3)-H alkenylation catalyzed by cationic alkylhafnium complexes: Stereoselective synthesis of trisubstituted alkenes from 2,6-dimethylpyridines and internal alkynes
Lopez, Michael J.,Kondo, Ai,Nagae, Haruki,Yamamoto, Koji,Tsurugi, Hayato,Mashima, Kazushi
, p. 3816 - 3827 (2016)
Dibenzylhafnium complexes 3a-d, supported by dianionic bidentate or tridentate ligands, upon activation via abstraction by either [Ph3C][B(C6F5)4] or B(C6F5)3 served as catalysts for the C(sp3)-H alkenylation of 2,6-dimethylpyridines with dialkylalkynes to give corresponding C(sp3)-H alkenylated products 6. Complex 3c, containing a pyridine arm in the ligand skeleton, exhibited the highest catalytic activity among 3a-d; initial addition of 2,6-dimethylpyridine (4a) to the C6D5Br solution of 3c followed by [Ph3C][B(C6F5)4] and 3-hexyne (5a) produced trisubstituted alkene 6aa in stereoselective manner in up to 50% yield without any byproducts, while the addition of 5a prior to 4a and [Ph3C][B(C6F5)4] to the C6D5Br solution of 3c generated 6aa, together with the formation of byproduct (E)-(2-ethylpent-2-en-1-yl)benzene (7). When an asymmetrical pyridine, 3-bromo-2,6-dimethylpyridine, was used as the coupling partner, the corresponding trisubstituted alkene was obtained selectively. Catalytically active cationic benzylhafnium complexes 8a-d, which were prepared by the reactions of 3a-d and B(C6F5)3, respectively, were characterized by 1H, 13C, and 19F NMR spectroscopy. Kinetic studies of the catalytic reaction between 4a and 4-octyne (5b) using 3c and [Ph3C][B(C6F5)4] in C6D5Br revealed that the catalytic reaction was zero-order for both 4a and 5b, indicating that the rate-determining step involved the C(sp3)-H bond activation of 4a by vinylhafnium intermediate 11c.
POTENTIAL ANTIHYPERTENSIVE AGENTS. SOME GUANIDINE DERIVATIVES.
BARRON,BAVIN,DURANT,NATOFF,SPICKETT,VALLANCE
, p. 705 - 711 (2007/10/05)
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