Structure of 1,1,1',1',3,3,3',3'-octamethyl-2,2'-biindanylidene, C26H32

Ideal Molecular Conformation versus Crystal Site Symmetry

“…Thus, the shortest C methyl –C methyl distances in the C i crystal conformations of 18 and 24 are 3.26 and 3.25 Å, respectively, but the same contact distances in their D 2 -symmetric ideal conformations are 3.34 and 3.31 Å, respectively. The more nearly rectangular structures of the C i conformations may permit tighter packing in the solid state , than would the chiral ground states.…”

“…Many of the same considerations that govern the conformations of p-sexiphenyl (12, discussed above) also apply to p-quinquephenyl (31), with the exception that the ideal conformation of 31 possesses C 2h symmetry. Because the crystal conformation possesses C i symmetry, a subgroup of C 2h , the structure does not appear anomalous on symmetry grounds.…”

Synthesis and Structural Assignment of Oxanilo-N-arylhydrazonoyl Chlorides

“…[3b, 10,22,27] In the IR spectra of chlorides 1b and 1k, recorded in CDCl 3 , this band was found. All the other IR spectra exhibited a band slightly shifted to lower wavenumber by about 10 cm Ϫ1 .…”

Carbenoid-mediated nucleophilic “hydrolysis” of 2-(dichloromethylidene)-1,1,3,3-tetramethylindane with DMSO participation, affording access to one-sidedly overcrowded ketone and bromoalkene descendants§

“…On the other hand, the somewhat alleviated internal repulsion in alkoxide 4 allowed it to be trapped by protonation below −10 °C before the cyclization could interfere [ 3 ], so that the resultant alcohol 5 could be isolated (crude yield 90% from 1,1,3,3-tetramethylindan-2-one) and dehydrated to give 2-(dichloromethylidene)-1,1,3,3-tetramethylindane ( 6 ) as the only product (97% yield). (ii) In X-ray diffraction analyses [ 4 – 9 ], the 1,1,3,3-tetramethylindan-2-ylidene parts turned out to be rather rigid, except for an occasional folding along the C-1/C-3 axis, and they did not exhibit the structural disorder problems and vexing angular flexibility which can arise with the t- Bu 2 C groups exemplified in Scheme 1 . (iii) Depending on the substituents at the exocyclic C-α atom in 7 , all four methyl groups in the 1,1,3,3-tetramethylindan-2-ylidene parts [ 10 ] and in their truncated analogue 1,1,3,3-tetramethylcyclopent-2-ylidene [ 11 ] may be nonequivalent and provide useful stereochemical and stereodynamic NMR information that would not be available from models containing the t- Bu 2 C moiety with free rotation about the t- Bu–C bonds.…”