Phane Hydrocarbons Containing Extended Arene Units

Phane Hydrocarbons Containing Extended Arene Units [Pg.9]

Consequently, two of the four protons of each ring (HA and HB) come to lie in the shielding anisotropy region of the opposite ring, thus absorbing as a high-field AB-pattern, which is further split by meta coupling (21 5 = 5.72 ppm 22 [Pg.10]

84 ppm). Protons Hr and HL do not experience any diatropic magnetic influence and appear in the typical arene proton range [AB-patterns, centered at 5 = 7.24 ppm (21) resp. 5 = 7.29 ppm (22)]. In 21, the rigid conformation not only differentiates HA and HB from HK and HL, but also the bridge protons Hx from Hy, creating an AA BB spin system centered at 5 = 2.82 ppm. [Pg.10]

The shift difference 6HA-5HB is significantly greater in triene 22 than in 21. [Pg.12]

The H—NMR-spectra of 21 resp. 22 remain unchanged up to at least 175 °C resp. 130 °C. This indicates a high conformational stability of the two phanes. The molecular propellers 45 21 and 22 belong to point group D3. Organic chemistry up to now only knows of four conformationally stable structures of this symmetry46-49. [Pg.12]

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