Experimental Enthalpies of Formation and Strain Energies for the Caged C20H20 Pagodane and Dodecahedrane Frameworks. [Erratum to document cited in CA122:80644]

Abstract

Calculated NMR structures had no NOE violations greater than 0.35 Á, rather than 3.5 Á as stated. JA955019USeven New Didemnins from the Marine Tunicate Trididemnum solidum [

Theoretical study on the coplanar double-cage dodecahedrane C35H30

“…The experimental heat of formation DH o f for C 20 H 20 and H 2 are 18.2 kcal mol À1 , 21 and zero, respectively. The energy change DH r of the reaction (1) has been calculated above.…”

Pentagonal dodecahedranes. Novel substitution patterns— MS fragmentation and unsaturation

“…1,6-Difluoroundecacyclo[9.9.0.0 2,9 .0 3,7 .0 4,20 .0 5,18 .0 6,16 .0 8,15 .0 10,14 . 0 12,19 .0 13,17 ]icosane 18 A suspension of dichloride 16 (33 mg, 0.1 mmol) and AgBF 4 (190 mg, 1.0 mmol) in CH 2 Cl 2 (3 ml)-diethyl ether (2 ml) was stirred at room temperature for 20 h (exclusion of light, total conversion, TLC). After addition of dry diethyl ether (10 ml) the organic phase was washed with water (2 × 10 ml), dried (MgSO 4 ) and filtered through a pad of silica gel (R f 0.58) to give 27 mg (93%) of colourless crystals, mp >300 ЊC; δ H (CDCl 3 ) see Table 1; δ C (CDCl 3 ) see Table 1; m/z 296 (82%, M ϩ ), 277 (4, M Ϫ F), 276 (9, M Ϫ HF), 275 (5), 183 (7), 167 (7), 165 (9), 159 (7), 149 (7), 137 (10), 135 (9), 123 (15), 115 (10), 109 (25), 97 (40).…”

“…Undecacyclo[9.9.0.0 2,9 .0 3,7 .0 4,20 .0 5,18 .0 6,16 .0 8,15 .0 10,14 .0 12,19 .0 13,17 Undecacyclo[9.9.0.0 2,9 .0 3,7 .0 4,20 .0 5,18 .0 6,16 .0 8,15 .0 10,14 .0 12,19 .0 13,17 ]-…”

“…Colourless crystals, mp 180-182 ЊC; ν max (KBr)/cm Ϫ1 1765 (C᎐ ᎐ O); δ H (CDCl 3 ) see Table 1; δ C (CDCl 3 ) see Table 1; 156.9 (q, C᎐ ᎐ O, 2 J C,F 41 Hz), 114.6 (q, CF 3 , 1 J C,F 287 Hz); m/z 484 (<1%, M ϩ ), 370 (95, M Ϫ CF 3 CO 2 H), 258 (8), 257 (52), 256 (100, M Ϫ 2 CF 3 CO 2 H), 255 (28), 241 (11), 215 (11), 178 (11), 165 (16), 153 (12), 141 (27), 128 (23), 115 (25). C 24 H 18 F 6 O 4 (484.4).…”

“…A structural feature of central importance within dodecahedrane chemistry is the rigid-ecliptical orientation of the external bonds (C᎐H, C᎐X/Y, A, B, C in Table 1). In fact, the molecular strain of the C 20 H 20 hydrocarbon (61.4 ± 1 kcal mol Ϫ1 ) 12 to a great part goes back to the non-bonded H,H interactions. There are therefore significant energetic costs to be paid for the replacement of hydrogens by larger substituents.…”