New polysubstituted monoterpenic thiazolidinones: synthesis, spectroscopic and crystal structure studies

The synthesis of three new polysubstituted monoterpenic thiazolidin‐4‐ones, namely ( Z )‐3‐methyl‐2‐{( E )‐[(1 R ,4 R )‐1,7,7‐trimethylbicyclo[2.2.1]heptan‐2‐ylidene]hydrazinylidene}thiazolidin‐4‐one, C 14 H 21 N 3 OS ( 2 ), (2 Z ,5 Z )‐5‐[(dimethylamino)methylidene]‐2‐{( E )‐[(1 R ,4 R )‐1,7,7‐trimethylbicyclo[2.2.1]heptan‐2‐ylidene]hydrazinylidene}thiazolidin‐4‐one, C 16 H 24 N 4 OS ( 3 ), and (2 Z ,5 Z )‐5‐[(dimethylamino)methylidene]‐3‐methyl‐2‐{( E )‐[(1 R ,4 R )‐1,7,7‐trimethylbicyclo[2.2.1]heptan‐2‐ylidene]hydrazinylidene}thiazolidin‐4‐one, C 17 H 26 N 4 OS ( 4 ), is reported, starting from the corresponding thiosemicarbazones obtained from naturally occurring ( R )‐camphor. All the newly obtained thiazolidin‐4‐ones have been fully characterized by HRMS and 1 H and 13 C (1D and 2D) NMR spectroscopy. Two of them, i.e. 2 and 3 , were identified by single‐crystal X‐ray crystallography, confirming the synthetic pathway and the spectroscopic analyses. In 3 , there are two roughly identical molecules within the asymmetric unit with the same absolute configuration. These two molecules are linked through N—H…O hydrogen bonds, building an R 2 2 (8) graph‐set motif.