Samarium(II)-promoted radical spirocyclization onto an aromatic ring |
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Authors: | Ohno Hiroaki Okumura Mitsuaki Maeda Shin-ichiro Iwasaki Hiroki Wakayama Ryutaro Tanaka Tetsuaki |
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Institution: | Graduate School of Pharmaceutical Sciences, Osaka University, 1-6 Yamadaoka, Suita, Osaka 565-0871, Japan. |
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Abstract: | Samarium(II)-mediated spirocyclization onto an aromatic ring was achieved by the reaction of methyl 4-(4-oxoalkyl)benzoates with SmI(2) in the presence of i-PrOH and HMPA, yielding methyl 1-alkyl-1-hydroxyspiro4.5]dec-6-ene-8-carboxylates in moderate to high yields. Utilizing this chemistry, spiro3.5] and -5.5] systems, and sterically congested spiro4.5] systems, were easily synthesized. For the successful conversion, appropriate activation of the aromatic ring has proven to be extremely important: while an ester or amide functionality on the aromatic ring can promote the spirocyclization, a sulfonamide substituent causes ortho cyclization. |
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