Cycloadditions. Part II. A steric effect in the 1,3-dipolar addition of 2-diazopropane to methyl but-2-ynoate
作者:A. C. Day、R. N. Inwood
DOI:10.1039/j39690001065
日期:——
5-methoxycarbonyl-3,3,4-trimethyl-3H-pyrazole being obtained in the ratio 6 : 1. In contrast, methyl propiolate behaves normally with 2-diazopropane, giving solely 3,3-dimethyl-5-methoxycarbonyl-3H-pyrazole. The preference for reverse addition to methyl but-2-ynoate is attributed to steric factors in the transition states for cycloaddition.
Cyclopropenes electrophiles : Reactions du morpholino-1 cyclohexene avec quelques esters GEM- DI methylcyclopropeniques; Acces a des analogues halopyrethriques (1).
作者:M. Franck-Neumann、M. Miesch、H. Kempf
DOI:10.1016/s0040-4020(88)90030-0
日期:1988.1
Electrophilic cyclopropene esters react with 1-morpholino cyclohexene to give various products depending on the second substituent of the cyclopropene double bond. Enamine alkylation is observed -but not always- as well as different formal cycloaddition reactions.
The photolysis of 3,3-dimethyl-3H-pyrazoles derived from 2-diazopropane and acetylenic esters and nitriles leads in good yields to electrophilic cyclopropenes Starting from acetylenic ketones, only the 4-keto-3H-pyrazoles give acylcyclopropenes, the photolysis of the 5-keto-derivatives leading mainly to vinylketenes.
Accès au squelette triquinanique linéaire par l'intermédiaire de dérivés bicyclo [2.1.0] pentaniques. Synthèse totale d'un triquinane, le (±) hirsutène.
作者:Michel Franck-Neumann、Michel Miesch、Eric Lacroix、Bernard Mertz、Jean-Marc Ken
DOI:10.1016/s0040-4020(01)88514-8
日期:1992.1
The cycloaddition of enamines with electrophilic gem-dimethylcyclopropenes followed by solvolytic ring cleavage of the 2-amino bicyclo [2.1.0] pentane adducts, leads to gem-dimethylcyclopentene derivatives. These reactions are used as key-sequence for the synthesis of Hirsutene, a natural linear triquinane, starting from the cyanocyclopropene 18 and the diquinane enamine 15. The cis-anti-cis-anti-cis
Cyclopropene als C<sub>3</sub>-Synthesebausteine: Cyclopentenole und große Ringe aus 2-Aminobicyclo[2.1.0]pentan-Derivaten über Ringerweiterungsreaktionen
Cyclopropenes as C3 Building Blocks: Cyclopentenols and Large Rings from 2-Aminobicyclo[2.1.0]pentane Derivatives via Ring-Enlargement Reactions The readily available methyl 3,3-dimethylcyclopropane-1-carboxylate undergoes [2+2] cycloaddition with enamines to give 2-aminobicyclo[2.1.0]pentane derivatives in moderate to good yields. These compounds are quantitatively transformed into 3-cyclopentenols by treatment with dilute mineral acids. From enamines derived from medium-ring ketones and morpholine, tricyclic adducts are formed, which eliminate morpholine under flash-thermolysis conditions at 600°C to give macrocycles containing an E double bond and an allenic system.