When arylmethyl 4-(sulfonyl)-3-butynyl ether and a catalytic amount of Rh(2)(tfa)(4) (tfa = CF(3)CO(2)-) were heated in toluene, 2-aryl-3-(sulfonyl)-5,6-dihydro-2H-pyran was produced in good yield. Ring closure proceeded in a highly regioselective manner, and no isomeric five-membered product was detected. Alternatively, 2-(5-sulfonyl-4-pentynyl)tetrahydrofuran lacking a benzyl substituent afforded a different product, 9-sulfonyl-1-hydroxy-8-nonen-4-one, upon reaction with the same rhodium catalyst at reflux in wet toluene. Both reactions most likely involve cleavage of the C-H bond alpha to ether in the substrate and subsequent intramolecular transfer of the hydrogen atom to sulfonylacetylene, which is supported by experiments using deuterium-labeled starting materials.

Redox reactions O 0225Rh-Catalyzed Isomerization and Intramolecular Redox Reaction of Alkynyl Ethers Affording Dihydropyrans and Ketoolefins. -Benzyl alkynyl ethers functionalized by a sulfone group react with formation of dihydropyrans. In the appropriate cases, the ring closure proceeds with high diastereoselectivity. Alkynyl ethers give ketoolefins as single geometric isomers. -(SHIKANAI, D.; MURASE, H.; HATA, T.; URABE*, H.; J. Am. Chem. Soc. 131 (2009) 9, 3166-3167; Dep. Biomol. Eng., Fac. Biosci. Biotechnol., Tokyo Inst. Technol., Midori, Yokohama 226, Japan; Eng.) -Klein 29-039

When an electrophile (H+ or an alkyl halide) was added to a mixture of 1-aryl-2-aza-1,3-butadiene and allyl Grignard reagent, selective assembly of the azadiene, nucleophiles, and an electrophile took place to give α,α′-diallylated amine in one pot.

Multicomponent reactions O 0359Electrophile-Triggered Assembly of Metal Enamides and Allyl Grignard Reagent in One-Pot. Novel Nucleophilic Double Allylation of Azadienes. -A one-pot multicomponent coupling process is based on a novel double αand α'-alkylation of azadienes with concomitant incorporation of an electrophile. The success of the process is based on the anomalous coupling of metal enamides and allyl Grignard reagents triggered by an electrophile. -(URABE*, H.; SHIKANAI, D.; ARAYAMA, K.; SATO, T.; TANAKA, R.; Chem. Lett. 36 (2007) 4, 556-557; Dep. Biomol. Eng., Fac. Biosci. Biotechnol., Tokyo Inst. Technol., Midori, Yokohama 226, Japan; Eng.) -R. Staver 39-052