Conversion of N-Allylaniline Promoted by Rh(I):¹ Synthesis and Molecular Structure of 2-Ethyl-1,2,3,4-tetrahydro-3-methyl-4-anilinoquinoline

N-Allylaniline (1) is converted catalytically into 2-ethyl-1,2,3,4-tetrahydro-3-methyl-4-anilinoquinoline (7) by Rh(I). The first step of the N-heterocycle ring synthesis is the isomerization of 1 into trans-N-prop-1-enylaniline (3). The cis isomer could be neither isolated nor detected in the reaction mixture. 1 and 3 undergo an intermolecular double-bond addition reaction promoted by Rh(I) to afford (Z)-2-methyl-1,3-dianilinopent-1-ene (6). A rhodium complex containing 6 as a chelate was isolated in combination with other complexes, and the diamine was displaced and characterized. The ring closure reaction to afford 7 goes most probably through ortho metalation of a phenyl ring. The nature of 7 was established from a single-crystal X-ray study; the molecular structure of 7 in solution was determined by NMR spectroscopy.