N-Alkylation of iodo lactams with reactive alkylhalides, or of the derived selenide lactams with less reactive alkylhalides, leads to substrates for free radical initiated cyclization to pyrrolizidinones and indolizidinones, e. g. 2 → 3. The first examples of iodide / vinyl bromide, selenide / aldehyde, and selenide / vinyl chloride radical cyclizations are described.
can reductively desymmetrize a large collection of easily available halomalonic esters to α-halo-β-hydroxyesters. These polyfunctionalized tertiary alkyl fluorides, chlorides, and bromides proved to be useful intermediates toward fluorinated drug analogs and polyhalogenated monoterpenes. The facile intramolecularepoxidation of the chiral chloride and bromide products has also enabled expeditious access
A concise totalsynthesis of rac‐alsmaphorazine D has been described for the first time. The efficient synthetic strategy features four key transformations: 1) a catalytic intramolecular oxidative cyclization for the δ‐lactamindole backbone; 2) an oxidative cyclic aminal formation for the hexahydropyrrolo[2,3‐b]pyrrole framework; 3) a transannular radical cyclization for the construction of the diazabicyclo[3
Hydrogen‐Atom‐Transfer‐Initiated Radical/Polar Crossover Annulation Cascade for Expedient Access to Complex Tetralins
作者:Lucas Johnson、Griffin Barnes、Sebastian Fernandez、Christopher D. Vanderwal
DOI:10.1002/anie.202303228
日期:——
A radical/polarcrossover manifold permits annulations between allylarenes and Giese-type accepters, providing a route to functionalized tetralins. The reaction conditions are mild and therefore exhibit significant functional group tolerance. The annulation products are formally cycloadducts of styrenes and electron-deficient alkenes, and they can be used to form a variety of strained ring products
Radical routes to indolizidines. Synthesis of (-)-slaframine
作者:Spencer Knapp、Frank S. Gibson
DOI:10.1021/jo00044a011
日期:1992.8
The synthesis of (-)-slaframine (5) was executed in 11 steps and 25% overall yield from resolved 3(S)-hydroxy-4-pentenamide (22). Two cyclization reactions were used to form the indolizidine skeleton and also to provide the necessary stereocontrol at C-8a and C-6 of the natural product. "Iodolactamization" of 22 gave selectively the cis-pyrrolidinone 21. Later in the synthesis, a silane-mediated radical cyclization of the phenylseleno lactam 33 gave selectively the 6-alpha-hydroxyindolizidinone 35a, an event predictable from model studies-such as 14c --> 15c. Replacement of hydroxy with azido and reduction of the lactam carbonyl gave "slaframine azide", 38, a stable and easily convertible immediate precursor to 5.