Diastereoselective Radical‐Mediated Hydrogen‐Atom Abstraction

Abstract

Es geht auch ohne Zinn: Eine Tandem‐Radikalreaktion führt zu optisch aktiven α‐Methylenlactonen wie 1. Die Radikal‐vermittelte Wasserstoffabstraktion von einem chiralen Acetal zu Beginn der Reaktion ist hochgradig stereoselektiv (siehe Schema). Das stereochemische Ergebnis einer solchen Reaktion hängt von ähnlichen Faktoren ab wie verwandte Cyclisierungen.

Effect of Brønsted acids on the thiophenol-mediated radical addition–translocation–cyclization process for the preparation of pyrrolidine derivatives

“…Alkenyl radicals can be generated directly from alkenyl halides [9,10] or by radical addition to a terminal alkyne [11][12][13][14][15][16][17][18][19]. The thiophenol-mediated radical addition-translocation-cyclization (RATC) process [20][21][22][23] is preparatively very useful since terminal alkynes are easily accessible [24]. It has been used to prepared simple and fused cyclopentanes as well as spirocyclic compounds such as (-)-erythrodiene [22,23,25].…”

Complete Regio‐ and Stereoselectivity Control in the Halohydroxylation of Non‐activated Allenes Mediated by a Remote Sulfinyl Group

“…Normally, mixtures of regioisomers are obtained unless the C=C=C system is polarized by strongly electron-donating [3] or electron-withdrawing groups. [4] Moreover, control of the stereoselectivity in allenic system is not an easy task, unless, a chiral center is directly connected to the reactive double bond. [5] On the basis of this prior knowledge, we envisioned that allenes 1 (Scheme 1) could be appropriate substrates for the remote control of both regio-and stereoselectivity of reactions taking place on the nonpolarized allenic systemsthe ability of the sulfinyl group to participate in anchimeric assistant is the controlling factor.…”