By Ring Expansion of a Pseudobase

A novel route to the rhoeadines starts with the readily available immonium salt 13 which was subjected to Schotten-Baumann conditions the aldehyde 15 was formed in 91% yield via the intermediate A-benzoylated pseudobase 14. Intramolecular aldol condensation of the aldehyde was induced by a strong base, thus generating the lactonic rhoeadine amide 16 in 56% yield. This short series of transformations represents a new benzazepine synthesis. 

Reduction with Redal (bismethoxyethoxyaluminum hydride) at 4° of tbe lactone 16 supplied the hemiacetal 17 which was 0-methylated and subjected again to Redal reduction, this time at 20°. The product was the secondary amine 18 which was A -methylated to the trans-fused rhoeadine analog 19 °  

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