Stereochemistry of 1,3-dipolar cycloaddition reaction of azomethine ylides derived from N-alkyl-N-(4-toluenesulphonyl) carbamoylmethyl phenanthridinium with olefinic dipolarophiles

A series of prepared N-alkyl-N-(p-toluenesulphonyl) bromoacetamides 1a-1b afforded with phenanthridine quaternary phenanthridinium salts 2a-2b. These, when treated with triethylamine in dichloromethane, form azomethine ylides that udergo cycloaddition reaction with present activated olefinic C=C double bond. This way pyrrolidino[1,2-f] phenanthridines 3-5 can be obtained. Their stereochemistry was studied by means of NMR spectroscopy. This family of phenanthridinium based ylides reacts very willingly with common olefinic dipolarophiles (dimethyl fumarate, dimethyl maleate or fumaronitrile) more or less stereoselectively. Some of the prepared racemic cycloadducts 3-5 were separated by HPLC on non-racemic cellulose-based sorbents with CD detection.