2H-1,2-Thiaborin: A New Boron–Sulfur Heterocycle

The reaction of 2,5-dihydro-2-diisopropylamino-1,2-thiaborole (5) with 2 equiv of LDA followed by CH₂Cl₂ gives 2-(diisopropylamino)-2H-1,2-thiaborin (2c), which has been spectroscopically and structurally characterized. DFT calculations indicate that formally aromatic 2c has a limited π-delocalized bonding in its heterocyclic ring.