Magnesium Halide-Catalyzed Synthesis of Oxaspiro[2.5]octenes from a Methylenecyclopropane and Acyl Cyanoalkenes
MgX2-catalyzed annulation of methylenecyclopropanes with acyl cyanoalkenes was accomplished to give oxaspiro[2.5]octenes in excellent yields. The reaction proceeded through a rare intramolecular oxa-Michael addition of Mg enolate. The oxaspiro
Substituent-Controlled Divergent Cascade Cycloaddition Reactions of Chalcones and Arylalkynols: Access to Spiroketals and Oxa-Bridged Fused Heterocycles
Herein, we report substituent-controlled divergent cascade cycloaddition reactions of chalcones and arylalkynols in the presence of PtI2. Depending on the substituent on the chalcone, either spiroketals or oxa-bridged fused heterocycles could be obtained in the ranges of 86–97% and 87–95% yields under identical reaction conditions. Control experiments were carried out to elucidate the origin of the high chemoselectivity. These provide a method for the synthesis of a diverse array of structurally complex oxygen-containing heterocycles. (Figure presented.).
Organocatalytic Asymmetric [4+2] Cycloaddition of 1-Acetylcyclopentene and 1-Acetylcyclohexene for the Synthesis of Fused Carbocycles
The first organocatalytic asymmetric [4+2]-cycloaddition reaction of 1-acetylcyclopentenes and 1-acetylcyclohexenes was developed. Enones having cyano groups were used as the dienophiles in this method. The reaction provides a useful practical route to th
Nath, Utpal,Pan, Subhas Chandra
supporting information
p. 6457 - 6461
(2017/12/01)
Tandem cross-Rauhut-Currier/cyclization reactions of activated alkenes to give densely functionalized 3,4-dihydropyrans
A novel tandem cross-Rauhut-Currier/cyclization reaction between α,β-unsaturated ketones was developed. Using DABCO (20 mol %) as the catalyst, a series of densely functionalized 3,4-dihydropyrans were obtained in excellent yields and stereoselectivities (up to 98% yield, >99:1 dr). A tentative catalytic cycle was proposed with key intermediates confirmed by ESIMS studies.
Liu, Wen,Zhou, Jing,Zheng, Changwu,Chen, Xingkuan,Xiao, Hua,Yang, Yingquan,Guo, Yinlong,Zhao, Gang
supporting information; experimental part
p. 1768 - 1773
(2011/04/15)
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