First friedel-crafts diacylation of a phenanthrene as the basis for an efficient synthesis of nonracemic

Reported are the first examples of Friedel-Crafts reactions used to prepare 3,6-diacylphenanthrenes. 9,10-Dimethoxyphenanthrene gives its 3,6-diacetyl derivative in good yield and in large amounts. The ketone's triisopropylsilyl enol ether when combined with 1, 4-benzoquinone forms a [7]helicenebisquinone. This bisquinone's reduction product, a bishydroquinone, when combined with methanolic HCl gives the [7]helicene whose peripheral side chains are all methoxyls but whose interior hydroxyls remain. The diastereomeric (1S)-(-)-camphanates can be separated by crystallization. Their structures, analyzed by X-ray diffraction, demonstrate that the camphanates' lactone functions point away from the ring system when the helicene has the (P) configuration and toward it when the helicene has the (M) configuration. This is because the camphanates' O=C-C-O dihedral angles are, as expected, close to 0 degrees in the former and close to 180 degrees in the latter. Other derivatives of 3,6-diacetylphenanthrene and of [7]helicenebisquinone are prepared, and the crystal structure of one of the latter is analyzed.

N- vs O-protonation and the transannular substituent interaction in 8-(Dimethylamino)-1-acetonaphthone

Dynamic NMR measurements of 8-(dimethylamino)-1-acetonaphthone 1 in neutral solutions reveal a solvent dependency of the barrier to NMe group interchange similar to that reported for N,N-dimethylacetamide. Titrating 1 with TFA in solvents of varying donicities gives rise to equilibrium mixtures of N-protonated aminoketone 2 and the O-protonated transannular addition product 3, the interconversion rate of which is slow on the NMR time scale at ambient temperature. The preference for O- or N-protonation is medium-dependent, the amount of N-protonated 2 increasing with a decrease in the nucleophilicity of the solvent. The set of equilibria which govern the interconversion of 2 and 3 in the titration mixtures are identified and their equilibrium constants evaluated from the NMR data. X-ray analysis of the crystalline trifluoroacetate salt of O-protonated 3 indicates that the transannular N.CO bond of 3 is formed to an extent of only 80%. The equilibrium distribution of 2 and 3, paired with the tetrafluoroborate anion, depends on both the nucleophilicity and the polarity of the solvent. In PhNO(2) the enthalpy change 3 --> 2 amounts to 2.6 kcal/mol.

Products from the reaction of meso-tetrakis(4-halophenyl)porphinato-manganese(II) and hexacyanobutadiene (HCBD): formation of pi-

The reaction of hexacyanobutadiene (HCBD) and meso-tetrakis(4-chlorophenyl)porphinatomanganese(II) pyridine [MnIITClPPpy] (1Cl) leads to two phases of [MnIIITClPPpy][HCBD].PhMe (alpha-2Clpy, beta-2Clpy). Similarly, the reaction of HCBD and tetrakis(4-bromophenyl)porphinatomanganese(II) pyridine [MnIITBrPPpy] (1Br) leads to two products [MnIIITBrPPpy] [HCBD] * PhMe (2 Brpy) and [MnIIITBrPP][HCBD]*2 PhMe (3Br). The structure of dark-green alpha-2Clpy consists of one porphyrin unit with MnIII in a square pyramidal coordination environment axially bound to one pyridine. The cation forms [MnIIITCIPPpy](2)2+ as cofacial dimerized porphyrins. Each [HCBD]*- is nonplanar with a torsion angle of 170.8(4) degrees about the center C-C bound, and forms [HCBD](2)2- dimers in the solid state with sub-van der Waals contacts of 3.325 and 3.340 angstroms. The magnetic data above 10 K obey the Curie-Weiss expression with a theta of -2.5 K, and mueff (300 K) = 4.91 muB as expected for S=2MnIII and S = 0 [HCBD](2)2-. The magnetic data for alpha-2Clpy can be fit with an zero-field-splitting D of -1.45 K. beta-2 Clpy consists of one porphyrin unit with MnIII in a distorted octahedral coordination environment axially bound to py and to a monodentate [HCBD]*- bound via an exo-nitrile. [HCBD]*- is nonplanar with a torsion angle of 169.7(5) degrees about the center C-C bound. The ueff (350 K) is 5.09 muB; however, the magnetic data do not obey the Curie-Weiss expression above 70 K. The low temperature data may be fit with a theta of -5.4 K. The data was modeled to an isolated S = 2 and S = 1/2 dinuclear spin system with J/kappaB = - 90 K. Decomposition of [HCBD]*- to [C4(CN)5O]- was evidenced by the determination of the structure of [MnIIITCIPP][C4(CN)5O] 2PhMe (3ClO). Crystals of 3 Cl-O were prepared by reaction of HCBD and 1Cl in the presence of a drop of water. The molecular structure consists of [HCBD]*-trans-mu-N-2,3-bound to [MnIIITBrPP]+ forming a 1-D coordination polymer of alternating [MnIIITBrPP]+ and [HCBD]*-. The intrachain Mn***Mn distance was 10.675(3) angstroms, with important interchain Mn***Mn distances of 10.832, 11.016, and 14.696 A. The magnetic data were fit to a Curie-Weiss law (10 < T< 290 K) with a theta of -3.5 K, and D = 0.3 K with mueff = 4.97 muB at 300 K.

Why (1S)-Camphanates Are Excellent Resolving Agents for Helicen-1-ols and Why They Can Be Used to Analyze Absolute Configurations.

The questions considered in this paper are why, as agents for resolving helicenols, camphanate esters are particularly effective, and why, in all 19 examples studied, when the (1S)-camphanates of (P)- and (M)-helicen-1-ols are chromatographed on silica gel, the former has the lower R(f)(). Models are proposed for the favored conformations of the esters, and to support the models, evidence is provided from five X-ray diffraction analyses and four ROESY analyses supplemented by molecular mechanics calculations. The essential discovery is that, presumably to avoid a steric interaction between a methyl on the camphanate's bridge and the helicene skeleton, the O=CCO conformation is anti-periplanar in (M)-helicenol camphanates and syn-periplanar in (P)-helicenol camphanates. In the former, the lactone carbonyl points toward the helicene ring system, and in the latter, it points away.

Two phases of

The solvent-bridged caesium phosphide [CsPH(eta6-2,4,6-(t)Bu3C6H2)]2(eta3-toluene)0.5x, catena-[(micro-eta3-toluene)-bis[caesium(2,4,6-tri-tert-butylphenylphosphide)]], undergoes a reversible solid-state, order-disorder phase transition characterized by the doubling of the unit-cell volume at low temperature achieved by doubling one unit-cell vector. The unit-cell parameters at 293 (2) K (form A) are: a = 11.147 (4), b = 14.615 (4), c = 14.806 (5) A, alpha = 70.57 (3), beta = 71.85 (3), gamma = 72.93 (2)degrees, V= 2112.5 (12) A3, Z = 2, rho(calc) = 1.362 g cm(-3), R1 = 0.0513 for 5462 reflections, wR2 = 0.0947 for all data. The unit-cell parameters at 173 (2) K (form B) are: a = 14.6241 (3), b = 14.7393 (3), c = 22.0720 (4) A, alpha = 72.2117 (7), beta = 73.3659 (8), gamma = 70.2953 (7)degrees, V = 4174.8 (2) A3, Z = 4, rho(calc) = 1.379 g cm(-3), R1 = 0.0405 for 14,010 reflections, wR2 = 0.1326 for all data. With a minor change, the key structural features discussed previously for form A [Rabe et aL (1998). Inorg. Chem. 37, 4235-4245] remain unchanged. The eta3-toluene ligand is observed to be disordered at 293 (2) K and ordered at 173 (2) K, with the order-disorder phase transition occurring at approximately 278 (2) K.

Enantioselective Total Synthesis of the Nonisoprenoid Sesquiterpene (-)-Kumausallene.

An acyl radical cyclization to form the bicyclic core of (-)-kumausallene (1) was the key feature in the 14-step, enantioselective synthesis. This work demonstrates that the bromoallene unit is robust enough to withstand multiple synthetic operations and provides the unambiguous assignment of the absolute configuration of the bromoallene.

Terthienyl-Based Redox-Switchable Hemilabile Ligands: Transition Metal Polymeric Complexes with Electrochemically Tunable or Switchable Coordination Environments?

By controlling the extent of oxidation of the polymeric forms of the new class of isolable, polymerizable terthienyl Ru(II) complexes 1, one can modulate both the binding strength of the polymer backbone for Ru(II) and the electronic nature of the bound metal centers.