ABSTRACT
This work reports the synthesis of new axially chiral bridged 2,2'-bipyridines 1 and pyridylmonooxazolines (pymox) 2. The potential of these new axially chiral N,N-ligands was evaluated in asymmetric catalytic cyclopropanation of styrene derivatives 22a-c with diazoesters 21a,b. While 2,2'-bipyridines 1a-c afforded the corresponding cyclopropanes 23a-f in up to 65% ee, pymoxs 2a-e gave somewhat lower enantioselectivities (up to 53% ee). Both classes of ligands produced trans-cyclopropanes 23a-f as the major isomer, although with modest diasteroselectivities (56 : 44 to 78 : 22). A structure-stereoselectivity relationship study of ligands 1 and 2 identified the chiral biaryl axis as being mostly responsible for the enantioselective performances of these ligands.
ABSTRACT
A very simple, safe and powerful method for the in situ generation of formaldehyde at low temperature in anhydrous conditions is described. This new tool avoids the use of gaseous formaldehyde and is suitable for basic carbon nucleophiles which cannot be generated in aqueous reaction media. Various substrates, including organolithium reagents and enolates, underwent smooth hydroxymethylation showing the versatility of this process. A Wittig reaction was also carried out in high yield. [reaction: see text]
ABSTRACT
A novel one-pot methodology is described for the synthesis of functionalized pyrrolopyridinones using in situ generated formimines and an ortho-lithiated pyridinecarboxamide species. Depending on the reaction conditions, this procedure allows versatile access to aminomethylated pyridinecarboxamides, 2,3-dihydro-pyrrolopyridinones, or 1,1-dialkylated 2,3-dihydro-pyrrolopyridinone derivatives. [reaction: see text]
