New Approach for the General Synthesis of Oxotetrahydroindoles via Intramolecular Cycloadditions of Azomethine Ylides with Tethered Alkynes
摘要:
A new method for the synthesis of oxotetrahydroindoles has been achieved employing an intramolecular dipolar cycloaddition approach involving mesoionic species (munchnones) with electron-deficient alkynes. The methodology is quite general and convergent as shown by the synthesis of a variety of tri- and tetrasubstituted oxotetrahydroindoles 18, 21, 24, 27, 30, and 34. LiI-based ester cleavage in the presence of an electrophilic acetylenic ketone was critical for formation of the requisite cycloaddition substrates. The cycloaddition is virtually unaffected by the presence of gem-dimethyl groups in the side chain (cf. 38). The presence of a substituted benzyl or a phenethyl moiety on nitrogen, a polarized acetylene, and an appropriate tether between dipole and dipolarophile are essential for obtaining optimal efficiency.
An efficient Synthesis of Acetylenic ?- and ?-Hydroxy Ketones, ?- and ?-keto acids, and ?- diketones via addition of 1-alkinyllithium compounds to ?- and ?-lactones
作者:Christine Wedler、Hans Schick
DOI:10.1002/prac.19933350503
日期:——
2-Hydroxy-6-alkyn-5-ones 3, 1-hydroxy-5-alkyn-4-ones 4, and 1-hydroxy-6-alkyn-5-ones 5 are conveniently obtained in exellent yields through a highly selective monoaddition of an 1-alkynyllithium compound 2 to gamma-valerolactone (1 a), gamma-butyrolactone (1 b) or delta-valerolactone (1 c). They are oxidized by pyridinium dichromate or Jones reagent to the corresponding acetylenic 1,4-diketones 6, 4-oxo carboxylic acids 7, and 5-oxo carboxylic acids 8, respectively.
Untersuchungen �ber die Bildung von 2-Acylcyclopentanonen aus 1-(1-�thynyl)-cyclopentenen und Perameisens�ure