N-heterocyclic carbene, high oxidation state molybdenum alkylidene complexes: functional-group-tolerant cationic metathesis catalysts

We synthesized the first N-heterocyclic carbene (NHC) complexes of Schrock's molybdenum imido alkylidene bis(triflate) complexes. Unlike existing bis(triflate) complexes, the novel 16-electron complexes represent metathesis active, functional-group-tolerant catalysts. Single-crystal X-ray structures of two representatives of this novel class of Schrock catalysts are presented and reactivity is discussed in view of their structural peculiarities. In the presence of monomer (substrate), these catalysts form cationic species and can be employed in ring-closing metathesis (RCM), ring-opening metathesis polymerization (ROMP), as well as in the cyclopolymerization of α,ω-diynes. Monomers containing functional groups, which are not tolerated by the existing variations of Schrock's catalyst, e.g., sec-amine, hydroxy, and carboxylic acid moieties, can be used. These catalysts therefore hold great promise in both organic and polymer chemistry, where they allow for the use of protic monomers.

Secretin, cholecystokinin and the biliary canalicular secretion in the rat

An attempt has been made to further assess which fraction of bile can be stimulated by the main gastrointestinal hormones in rats. In the cannulated conscious animals the i.v. infusions of glucagon, impure Boots secretin, impure Boots cholecystokinin (CCK) and OP-CCK resulted in 8.9% (N.S.), 68.5% (P < 0.001), 88.7% (P < 0.001) and 19.0% (P < 0.05) increase in the estimated bile acid-dependent bile flow (BAF) and in 25.4% (P < 0.01), 49.2% (P < 0.001), 44.5% (P < 0.001) and 1.6% (N.S.) increase in the estimated bile acid-independent bile flow (BAIF), respectively as compared to the control values. When the calculated BAF values corresponding to the bile acid impurities in Boots secretin and Boots CCK were subtracted from BAF and BAIF values obtained during hormone infusions (the corrected values), the increase in both BAF and BAIF was equal to 38.9% (P < 0.02) and 29.4% (P < 0.02) during Boots secretin infusion and to 61.1% (P < 0.01) and 29.4% (P < 0.02) during Boots CCK infusion, respectively as compared to the control values. It can be suggested that the hormonal impurities in the Boots preparations interacting with the principal hormonal component are able to stimulate BAF in the rat. Further extensive study embracing the interactions of the purified gut hormones may confirm their role in the control of canalicular bile secretion in the rat.