Primary alkylamines 1 and hindered arylamines 1 give high yields of isocyanates 5 when reacted with carbon dioxide and the Mitsunobu zwitterions 4 generated from dialkyl azodicarboxylates and Bu 3 P in dichloromethane at -78 °C. Use of Ph 3 P still gave high yields of isocyanates from reactions of primary alkylamines, but only low yields were obtained from reactions of aromatic amines. Reactions which failed to give high yields of isocyanates gave either carbamoylhydrazines 6 and/or dicarbamoylhydrazines 10 and/or triazolinones 7. The triazolinones were shown to arise from reactions of reactive aryl isocyanates with the Mitsunobu zwitterion. The carbamoylhydrazines were shown not to arise from reaction of isocyanate with reduced dialkyl azodicarboxylates, and a mechanism for their formation is proposed. Single-crystal X-ray analyses confirmed the structures of 6, 7, and 10. 3940
Rhodium-catalysed reactions of N-benzyl- or
N-alkyl-aminoalkenes (6) with
H2/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 H2/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.
Asymmetric alcohols were resolved as 1-a-O-alkyl-2,3-unsaturated hexosides. After separation of diastereoisomers, the auxiliary and the enantiomeric alcohol were recovered by transglycosidation. Potential applications include resolution of labile secondary and tertiary alcohols, difficult by existing techniques, and enhancement of ees of chiral alcohols produced enzymatically or by synthetic catalytic methods.
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.