Use of Imidazo[1,5‐
<i>a</i>
]pyridin‐3‐ylidene as a Platform for Metal‐Imidazole Cooperative Catalysis: Silver‐Catalyzed Cyclization of Alkyne‐Tethered Carboxylic Acids
Silver complexes with 5‐(4‐(tert‐butyl)‐1H‐imidazol‐1‐yl)‐imidazo[1,5‐a]pyridin‐3‐ylidene ligands were synthesized as metal‐imidazole acid‐base cooperative catalysts. Single crystal XRD analysis revealed that the silver atom was located in the vicinity of the imidazole ring and that cationic silver complexes formed dimers through coordination between the silver metal and the imidazole pendant. These
Cyclization of alkynoic acids with gold catalysts: a surprising dichotomy between AuI and AuIII
作者:Hassina Harkat、Albert Yénimégué Dembelé、Jean-Marc Weibel、Aurélien Blanc、Patrick Pale
DOI:10.1016/j.tet.2008.10.112
日期:2009.2
ω-Acetylenic acids, substituted or not at their acetylenic end, could be efficiently cyclized to γ- or δ-alkylidene lactones in the presence of AuCl and K2CO3. In contrast AuCl3 led to lactone dimers, probably through cyclization and reductive dimerization. These AuI and AuIII catalyzed cyclizations were totally regioselective and most often highly stereoselective.
在AuCl和K 2 CO 3的存在下,可以在其乙炔基末端取代或不取代的ω-乙炔酸有效地环化为γ-或δ-亚烷基内酯。相反,AuCl 3可能通过环化和还原性二聚而导致内酯二聚体。这些Au I和Au III催化的环化反应完全是区域选择性的,并且通常是高度立体选择性的。
PALE, PATRICK;CHUCHE, JOSSELIN, TETRAHEDRON LETT., 28,(1987) N 51, 6447-6448