A number of 1-alkenyl sulfoxides bearing either a diphenylmethyl (DPM) or a p-methoxybenzyl (PMB) group have been prepared and exposed to the chlorine surrogate SO2Cl2. Through an oxidative fragmentation reaction, a new family of sulfur acid derivatives, 1-alkenesulfinyl chlorides, is generated. They can be characterized by IR spectroscopy before chemical capture with an alcohol. Ethenesulfinyl chloride (2a) and 1-propenesulfinyl chloride (2b), obtained from their corresponding DPM precursor, can be distilled at reduced pressure to afford ca. 90% pure material. NMR chemical shift comparison of various 1-alkenesulfinyl-containing compounds is made. 1-Alkenesulfinylmethyl phenyl(alkyl) ketones (6) can be prepared directly from sulfinyl chlorides 2 although decomposition and/or isomerization is sometimes extensive during purification.

Can. J. Chem. 69,404 (1991). For the title systems, single crystal X-ray data indicate the presence of totally asymmetric structures. These features are reflected in the multiplicity of resonances in the solid phase I3C NMR spectra. Some of the I3c chemical shift trends are analyzed in terms of torsional angle influences. In solution, resonance assignments have been made with the aid of 2D methods. Stereochemical inferences are drawn from NOESY spectra and 'H-'H couplings. Low temperature solution experiments indicate that conformational interconversions in both the free ligand and the NaNCS complex are rapid on the NMR timescale down to 163 K.

Regiospecifically substituted 2-hydroxybenzocyclobutenones were synthesized from the corresponding TBS protected 2-bromo-mandelate esters via halogen–metal exchange, cyclization, and subsequent deprotection. Keywords: 2-hydroxybenzocyclobutenones, halogen–metal exchange, benzocyclobutenediones, 2-bromomandelate esters.

Ethyl (Z)-2-carbomethoxyethenesulfinate (1) and ethyl (E)-2-carbomethoxyethenesulfinate (2) were each subjected to cyclopentadiene (ca. 3 equiv) in order to determine their reactivity in Diels-Alder reactions. Thermal reactions proceeded in less than 4 h, while Lewis Acid enhanced reactions were substantially faster and demonstrated greater selectivity. In particular, the BF(3).Et(2)O-mediated cycloaddition of 1 gave syn/endo cycloadduct 3a as a major diastereomer in about 90% yield. The reactions of 2 were less synthetically useful. The structures of the cycloadducts were established through a combination of X-ray crystal structure determinations and through exposure of the compounds to an electrophilic iodine reagent. Each cycloadduct underwent an iodocyclization reaction with either the carboxylic ester or the sulfinate ester participating in the formation of a polycyclic lactone or sultine, respectively. The iodocyclization reactions allowed further elucidation of the cycloadduct structures.

Several C-4 carbon-substituted analogues of podophyllotoxin, 1, were prepared by treatment of 1 with allyltrimethylsilane or trimethylsilylcyanide in the presence of boron trifluoride etherate. Alternatively, carbon substituents were introduced via additions to the carbobenzyloxy-protected C-4'-dimethylated podophyllotoxone. These 4'-dimethylated derivatives showed promising in vitro antitumour activity and were equally active against human colon cell line HT116 and two multidrug resistant cell lines. The alcohol 6 was evaluated in vivo but was found to be inactive.

Can. J. Chem. 70, 1688 (1992. The major isomer obtained by hydrogenation of dibenzo-24-crown-8 ether is shown to have the cis-syn-cis configuration as determined from the crystal structure of its sodium perchlorate complex. This material possesses eight-coordinate sodium with Na-0 distances ranging from 2.54 to 2.78 A. The complex is shown to exist in a single asymmetric conformation below 240 K as determined by I3C NMR at 125 MHz. From NMR coalescence temperature measurement, the free energy of activation for cyclohexane ring inversion in this complex has been determined to be 51.0 * 1688 (1992). En se basant sur la structure cristalline du perchlorate, on a determine que l'isomkre majeur obtenu par hydrogenation de 1'Cther dibenzo-24-couronne-8 posskde la configurati~n~cis-syn-cis. Dans ce produit, il y a huit atomes de sodium de cordonnes et les distances Na-0 varient de 2,54 a 2,78 A. Grice a la RMN du I3C a 125 MHz, on a dCmontr6 que, 2i une temperature inferieure 240 K, le complexe existe sous une seule conformation asymetrique. Sur la base de mesures de temperatures de coalescence, on a determine que l'energie libre d'interconversion du cyclohexane est egale 2i 51,O c 0,6 kJ/mol.[Traduit par la redaction]

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