Tetraalkylidene‐1,4‐diboracyclohexanes from 3,4‐Dilithio‐2,5‐dimethyl‐2,4‐hexadiene; the First “Hetero[6]radialene” with Chair Conformation

The tetrapropylidenediboracyclohexanes 2a, b are stable toward air and moisture. They were obtained from 1 and the corresponding dihaloborane at − 50°C in Et2O. According to the X-ray structure analysis, 2a adopts the chair conformation, in contrast, for example, to 2c. Boracyclopropanes could not be detected as the initial products.