Alanes pyridines

The pyridine ring is easily reduced in the form of its quaternary salts to give hexahydro derivatives by catalytic hydrogenation [446], and to tetrahydro and hexahydro derivatives by reduction with alane aluminum hydride) [447], sodium aluminum hydride [448], sodium bis 2-methoxyethoxy)aluminum hydride [448], sodium borohydride [447], potassium borohydride [449], sodium in ethanol [444, 450], and formic acid [318]. Reductions with hydrides give predominantly 1,2,5,6-tetrahydro derivatives while electroreduction and reduction with formic acid give more hexahydro derivatives [451,452]. 

Financial support was provided by the National Science Foundation (Grant CHE-94-13128). Prof. Alan Bond and Mr. Richard Webster provided advance information concerning their studies on the electrochemistry of pyridine 2,6-dithioesters and related substances84. 

Donor-r acceptor (D-rA) interactions. The combination of donor and acceptor sites raises the possibility of D A interactions (intramolecular and intermolecular). In most systems, such D A interactions are prevented by the steric demand of the substituents (steric frustration) and/or the nature of the organic linker (geometric frustration). Noticeable exceptions are illustrated in Scheme 1 (i) the Cj-bridged phosphine-alane 3 adopts a head-to-tail dimeric structure and is usually reacted in the presence of an additional Lewis base to displace the A1 interactions " (ii) the di- and tri-phosphine boranes 7 and 8 equilibrate in solution between open and closed forms which were unambiguously identified in the solid state by X-ray diffraction analyses (iii) the pyridine-borane 2 exists in solution as a mixture of closed monomeric form and head-to-tail dimeric structure, but N B interactions are readily cleaved upon coordination to Ru. ... 

The Lansbury reagent, formed as the product of the reaction between pyridines with lithium tetrahydroaluminate (Hthium alanate), has been employed as a useful reducing agent in organic chemistry for a long time. Hensen and coworkers demonstrated that Lansbury reagent has the... 

---