109432-97-5Relevant academic research and scientific papers
A rhodium catalyzed cycloisomerization and tandem Diels-Alder reaction for facile access to diverse bicyclic and tricyclic heterocycles
Zhou, Yirong,Nikbakht, Ali,Bauer, Felix,Breit, Bernhard
, p. 4805 - 4810 (2019)
A regioselective distal cycloisomerization of 1,6-allenenes was successfully developed to afford six-membered ring exocyclic 1,3-dienes employing a rhodium/diphosphine catalyst system. Deuterium labelling experiments and DFT calculations were performed to provide insights into the reaction mechanism of this unprecedented transformation. In addition, one-pot tandem Diels-Alder reactions with various dienophiles could readily construct diverse bicyclic and tricyclic nitrogen heterocycles, which are ubiquitous core scaffolds for a variety of natural products and bioactives. High efficiency and exclusive chemo and regioselectivities for a broad substrate scope were achieved under mild conditions using a low catalyst loading of 0.5 mol%.
Pd-catalyzed cycloisomerization to 1,2-dialkylidenecycloalkanes. 2. Alternative catalyst system
Trost, Barry M.,Romero, Donna L.,Rise, Frode
, p. 4268 - 4278 (2007/10/02)
The mechanisms by which palladium complexes may catalyze the cycloisomerization of 1,6- and 1,7-enynes to dialkylidenecycloalkanes were probed by exploring a catalyst system different than a ligated palladium acetate which previously has proven to be successful. Although carboxylic acids showed no discernible interaction with palladium(0) complexes, this combination proved to be a powerful catalyst system to effect this cycloisomerization. The fact that the two catalyst systems do not have the same reactivity profile suggests this new catalyst system may operate by a different mechanism. Evidence supporting a pathway invoking formation of a hydridopalladium acetate followed by hydropalladation as initiation is presented. Steric and electronic effects direct the regioselectivity of the termination step to form either 1,3- or 1,4-diene products. The 1,3-diene products participate exceedingly well in Diels-Alder reactions, both inter- and intramolecularly. The presence of an oxygen substituent at the position allylic to the diene served as both a regiochemical control element for the palladium-catalyzed cycloisomerization and a diastereochemical control element for the Diels-Alder reaction. The net result of these two steps the first of which is a catalyzed isomerization and the second an addition, is a highly efficient approach to complex polycycles in terms of both selectivity and atom economy.
A NEW PALLADIUM CATALYST FOR INTRAMOLECULAR CARBAMETALATIONS OF ENYNES
Trost, Barry M.,Lee, Donna C.,Rise, Frode
, p. 651 - 654 (2007/10/02)
The combination of (dba)3Pd2*CHCl3 plus a carboxylic acid effectively catalyzes cyclization of 1,6-enynes in which asymmetric induction may be achieved by use of enantiomerically pure carboxylic acids.
