Irradiation of 2,4-cyclooctadienone (1) in benzene or toluene is shown to give in >80% yield two headto-head dimers. The ring fusions are shown to occur at the a,P-positions of the dienone with trrrns-cis and trans+inti-trrzns stereochemistry. Both dimers may be epimerized to the same product withcis+rnti-cis ring fusions. Evidence is presented to show that the singlet state is responsible for the cis4rritls isomerization of 1 to the highly reactive intermediate trans,cis-2,4-cyclooctadienone. This intermediate can dimerize in a thermal 2 + 2 cycloaddition or can be generated at -78" and then trapped by 1,3-dienes in a Diels-Alder reaction. A mechanism for the dimerization reaction is discussed. L'irradiation de la cyclooctadiene-2,4 one (1) dans le benzene ou le toluene conduit a deux dimeres t2te-t2te avec un rendement >80%. Les fusions de cycle se produisent sur les positions a,@ de la dienone avec la stCreochimietrnt~s-cis et trrins+~tzti-trans. Les deux dimtres peuvent 2treCpimCrisCs enun mimeproduit avec des fusions de cycle cis-unti-cis. L'Ctat singulet responsable de I'isomtrisation cis--trut~s de 1 e n un intermtdiaire hautement rCactif trrrns-cis cyclooctadiene-2,4 one, a CtC prouvC. Cet intermkdiaire peut se dimeriser selon une cycloaddition [2 + 23 thermique ou bien engendre -78" puis pikge par des dienes-1,3 selon une reaction de Diels Alder. Un mecanisme pour la reaction de dimCrisation a Cte discutk.[Traduit par le journal]Can.

During the 27-month period between January 1, 1992, and March 31,1994, Agriculture and AgriFood Canada analyzed 21 982 samples of fruit and vegetable commodities for pesticide residues. A multiresidue method capable of detecting over 200 analytes was used. In 5784 domestic samples a total of 676 residue findings were made. Of these, 32 (0.55%) were in violation of Canadian maximum residue limits (MRLs).In 16 198 imported products, 464 of 3193 residue findings exceeded MRLs, corresponding to a violation rate of 2.86%. One-half of domestic violations resulted from commodity–pes ticide combinations for which there are no Canadian approvals.

The first total synthesis of the spirosesquiterpene (−)-acorenone (1) is described. The critical step involves a spiroannelation of the enamine of aldehyde 11 with 1-methoxy-3-buten-2-one (16) in the presence of acetic acid to give ketone 17. Reaction of 17 with methylmagnesium iodide followed by treatment of the resultant alcohol 18 with p-toluenesulfonic acid in refluxing benzene leads directly to 1 in good overall yield. As the starting material for the preparation of the cyclopentanoid aldehyde 11 was (+)-limonene the final product is optically active and thus the absolute configuration of naturally occurring (−)-acorenone (1) is established. The preparation of a number of other optically active cyclopentanoid monoterpenes (4 and 13) is also described.

, and WAH-PIu TANG. Can. J. Chem. 57,904 (1979).Several synthetic routes to some new substituted pyrazol-4-01s and the reactions: methylation, acetylation, Michael addition, and oxidation are reported. Synthesis and cycloaddition reactions of the systems pyrazolium-4-olate and 3,4-diazacyclopentadienone are also reported. The former does not cycloadd, whereas the latter behaves as both a diene and a dienophile in various cycloadditions.

An analytical method for the identification of the residues from 14 commonly used antibiotics is presented. The technique is based on selective tissue extraction followed by thin layer chromatography (TLC)/bioautography. Antibiotic residues are extracted from the tissues with methanol and methanol-HCl (98 + 2). The methanol extract is further extracted with chloroform to isolate groups of antibiotics. The extracts are spotted onto TLC plates and developed in suitable solvent systems. Developed plates are placed on set medium seeded with Bacillus subtilis and a bioautograph is produced. The locations of zones of inhibition are used to identify antibiotic residues. Recoveries of antibiotics were quantitative, while the effect of naturally inhibiting components of the matrix was minimized. The sensitivity of the method can be adjusted through minor modifications, which allows its use in routine regulatory analysis.