ChemInform Abstract: Lewis Acid-Induced Synthetic Equivalents of Imines and Iminium Ions. Part 13. Cycloaddition of Lewis Acid-Induced N-Methyleneanilines as Azadienes to 1,2-Bistrimethylsilyloxycyclobutene and Oxidative Ring Expansion to 1,2,4,5-Tetrahyd

ChemInform ◽  
2001 ◽  
Vol 32 (16) ◽  
pp. no-no
Author(s):  
Hyun-Joon Ha ◽  
Chang-Ju Choi ◽  
Young-Gil Ahn ◽  
Hoseop Yun ◽  
Yongkwan Dong ◽  
...  
Keyword(s):  
Lewis Acid ◽  
Ring Expansion ◽  
Iminium Ions ◽  
Oxidative Ring Expansion

scholarly journals Oxidative Ring Expansion of Cyclobutanols: Access to Functionalized 1,2-Dioxanes

2020 ◽  
Author(s):  
María Martín López Martín López ◽  
Nicolas Jamey ◽  
Alexis Pinet ◽  
Bruno Figadère ◽  
Ferrié Laurent
Keyword(s):  
Total Synthesis ◽  
Lewis Acid ◽  
Ring Expansion ◽  
Alkoxy Radical ◽  
Tertiary Alcohols ◽  
Radical Traps ◽  
Oxidative Ring Expansion

Cyclobutanols undergo an oxidative ring expansion into 1,2-dioxanols by using Co(acac)<sub>2</sub> and triplet oxygen (<sup>3</sup>O<sub>2</sub>) as radical promoters. The formation of an alkoxy radical drives to the regioselective break of the strained ring with stabilization of a new radical on the most substituted side. The radical traps then oxygen to form 1,2-dioxanols. The reaction is particularly effective on secondary cyclobutanols but can work also on tertiary alcohols. Further acetylation generates peroxycarbenium species under catalytic Lewis acid conditions, which react with neutral nucleophiles. Many original 1,2-dioxanes, which would be difficult to prepare by another method, were then obtained with a preferred 3,6-<i>cis</i>-configuration. This method provides an interesting access to the total synthesis of many natural endoperoxides.

scholarly journals Oxidative Ring Expansion of Cyclobutanols: Access to Functionalized 1,2-Dioxanes

2020 ◽  
Author(s):  
María Martín López Martín López ◽  
Nicolas Jamey ◽  
Alexis Pinet ◽  
Bruno Figadère ◽  
Ferrié Laurent
Keyword(s):  
Total Synthesis ◽  
Lewis Acid ◽  
Ring Expansion ◽  
Alkoxy Radical ◽  
Tertiary Alcohols ◽  
Radical Traps ◽  
Oxidative Ring Expansion

Cyclobutanols undergo an oxidative ring expansion into 1,2-dioxanols by using Co(acac)<sub>2</sub> and triplet oxygen (<sup>3</sup>O<sub>2</sub>) as radical promoters. The formation of an alkoxy radical drives to the regioselective break of the strained ring with stabilization of a new radical on the most substituted side. The radical traps then oxygen to form 1,2-dioxanols. The reaction is particularly effective on secondary cyclobutanols but can work also on tertiary alcohols. Further acetylation generates peroxycarbenium species under catalytic Lewis acid conditions, which react with neutral nucleophiles. Many original 1,2-dioxanes, which would be difficult to prepare by another method, were then obtained with a preferred 3,6-<i>cis</i>-configuration. This method provides an interesting access to the total synthesis of many natural endoperoxides.

The oxidative ring expansion of spiro-annulated chroman-4-ones: Syntheses of the rotenoid core and related benzoxanthones

1998 ◽  
Vol 39 (8) ◽  
pp. 881-884 ◽  
Author(s):  
Christopher D. Gabbutt ◽  
John D. Hepworth ◽  
B. Mark Heron ◽  
Jean-Luc Thomas
Keyword(s):  
Ring Expansion ◽  
Oxidative Ring Expansion
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