Terpenes U 0200Synthesis, Structure, and Absolute Configuration of a New Cyclopropanic Compound Derived from the Sesquiterpene β-Himachalene. -Cyclopropanation of the bridgehead double bond of β-himachalene (I) with dichlorocarbene, generated in a phase-transfer-catalytic system, followed by oxidative cleavage of the cyclohexene double bond in (III) yields the polyfunctionalized enantiopure dichlorocyclopropane (IV), which could be a valuable precursor for pyrethroid derivatives. Its absolute configuration is determined by means of an X-ray single-crystal structure analysis. -(ZIYAT, H.; EL HOUSSAME, S.; ALI, M. A.; ITTO, M. Y. A.; KARIM, A.; WARTCHOW, R.; BUTENSCHOEN, H.
Organo-silicon compounds S 0060 Stereodivergent Formation of Alkenylsilanes: syn or anti Hydrosilylation of Alkynes Catalyzed by a Cyclopentadienylcobalt(I) Chelate Bearing a Pendant Phosphane Tether. -The hydrosilylation of internal symmetrical alkynes with silane (II) affords exclusively syn-hydrosilylation products, whereas with silane (IV) anti-hydrosilylation predominates. Unsymmetrical internal alkynes react with exclusive syn-hydrosilylation and low regioselectivity. The reaction of terminal alkynes with (II) is less selective and their treatment with (IV) results in cyclotrimerization. -(YONG, L.; KIRLEIS, K.; BUTENSCHOEN*, H.; Adv. Synth. Catal. 348 (2006) 7-8, 833-836; Inst. Org. Chem., Univ. Hannover, D-30167 Hannover, Germany; Eng.) -Klein 37-145
Organo-chromium compounds S 5500Unanticipated Formation of ortho-Sulfone Substituted Phenols by Anionic Thia-Fries Rearrangement of (Aryl triflate)tricarbonylchromium Complexes. -Tricarbonylchromium complexes of aryl triflates (V), (VII), (IX) and (XI) undergo base-mediated anionic thia-Fries rearrangement to generate push-pull substituted ortho-(trifluoromethylsulfonyl)phenol complexes (VI), (VIII), (X) and (XII) under very mild conditions. This pathway is in contrast to the chemistry of the uncomplexed ligand systems, which usually react with benzyne formation. -(ZHAO, Z.; MESSINGER, J.; SCHOEN, U.; WARTCHOW, R.; BUTENSCHOEN*, H.; Chem. Commun. (Cambridge) 2006, 28, 3007-3009; Inst. Org. Chem., Univ. Hannover, D-30167 Hannover, Germany; Eng.) -M. Paetzel 48-184
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