Interaction of sulfur dioxide with 1-benzyl-1,4-dihydronicotinamide

A Diels–Alder approach for the synthesis of highly functionalized benzo-annulated indane-based α-amino acid derivatives via a sultine intermediate

“…Several attempts to generate o-xylylene intermediate 8 from the dibromide 7 under different reaction conditions 10 were unsuccessful (Scheme 2). Reaction of the dibromide 7 with sodium hydroxy methanesulfinate (rongalite) 11 in the presence of tetrabutylammonium bromide (TBAB) in DMF at 0°C gave isomeric sultinebased AAA derivatives 9 (mp 180-181°C) and 10 (mp 198-199°C) in 72% combined yield (1:1). The two isomers 9 and 10 have very similar IR, 1 H NMR, 13 C NMR, HRMS, and UV spectra and it was not possible to assign their exact stereochemistry with the available data.…”

A Convenient Synthesis of 2,2′,6,6′-Tetramethyl-4,4′-bipyridine and Its Oxidation to 2,2′,6,6′-Tetracarboxy-4,4′-bipyridine

“…Sulfur dioxide has occasionally been employed as a dehydrogenating agent for 1,4-dihydropyridines 8 and N,N -dialkyl-4,4'-tetrahydrobipyridines. 9 ,lo Up to now, one can only specula.te on the reaction course.…”