Rhodium-catalysed reactions of N-benzyl- or N-alkyl-aminoalkenes (6) with H 2/CO can give cyclic amines (7) (7-13 ring size) in good to excellent yields when BIPHEPHOS is used as a ligand. Hydrogenation of the aminoalkene becomes a competing reaction for the smaller rings but can be overcome by using a H 2/CO gas ratio of 1:5. Reactions of 2-alkenyloxybenzylamines (13) gave 9-, 12- and 17-membered rings (14) in 30-40% yield, but dimer formation (16) and/or hydrogenation were competing reactions. Similar reactions of alkenylamides and ortho-alkenylanilines gave only non-cyclized amino aldehydes as products in low isolated yields.
- Cyclic amines
- Rhodium catalysts