NEW CHIRAL HETEROCYCLES - 5-[(R)-(-1'-METHYLBENZYL]-1,3,5-DITHIAZINE AND )-1'-METHYLBENZYL]-3,7-DIAZA-1,5-DITHIACYCLOOCTANE - CONFORMATIONAL STUDIES AND THEIR REACTIONS WITH BORANE())

We report herein the syntheses of a new 5-[(R)-(+)-1'-methylbenzyl]-1, 3,5-dithiazine 1, the 5-isopropyl-1,3,5-dithiazine 2 and the )-1'-meth ylbenzyl]-3,7-diaza-1,5-dithiacyclooctane 3, two of them (1 and 3) are new sulfur and nitrogen heterocycles bearing a chiral N-substituent. Compounds 1 and 2 were found in conformational equilibrium when observ ed at rt at H-1-270 MHz or C-13-67.8 MHz, when cooling a preferred cha ir conformation was observed with the N-substituent in the axial posit ion. Heterocycle 3 was in an anchored crown conformation at rt. A conf ormational study of ring inversions for 1 and 3 was performed and thei r thermodynamic data were obtained, Delta G = 48.1 +/- 0.8 for 1 and Delta G = 64.8 +/- 1.2 kJ/mol for 3. The reactivity of 1-3 with BH3-T HF was investigated, the N- or S-BH3 adducts were not stable, the reac tions afforded cleanly the N-borane-N-dimethyl-N-alkylamine adducts. T he reaction of 3 with BD3 gave the N-BD3 adduct of [CH2D]2N-CH[CH3]C6H 5. An X-ray diffraction study of 3 confirmed its crown conformation wi th the N-substituents in pseudo-axial position.