N,Se-Acetals: Preparation and use in diastereoselective radical reactions
作者:Aleksandar Stojanovic、Philippe Renaud
DOI:10.1002/hlca.19980810216
日期:1998.2.4
3–5). These acetals are used as precursors for stereoselective radical deuteration and allylation reactions (Schemes 6 and 7, Tables 1 and 2). The stereochemical outcome of the reactions depends on the radical trap and the substituents at the N-atom. Deuterations give always anti products with moderate to high selectivities. The allylation reactions give either syn or anti products with low to moderate
Generation of 1-Amidoalkyl Radicals from N-Protected Amino Acids: An Alternative to the Barton Decarboxylation Procedure
作者:Aleksandar Stojanovic、Philippe Renaud
DOI:10.1055/s-1997-727
日期:1997.2
An alternative method to the Barton decarboxylation procedure of N-protected amino acids is presented. The carboxylic acids are transformed into stable phenylselenoesters. Upon standard radical reaction conditions, they generate acyl radicals which undergo a very fast decarbonylation reaction to N-protected 1-aminoalkyl radicals. The decarbonylated radicals are trapped reductively and by intermolecular additions to olefins.
thane has been demonstrated to be a highly versatile gem-difluoromethylene (CF2) buildingblock via the reaction of difluorophenylsulfanylmethyl radical with olefins. gem-Difluoroalkenes and products containing a midchain CF2 group and with manipulatable functionality can be readily synthesized. The first example of a gem-difluoromethylene radical synthon is also reported.
A systematic investigation of radical haloacetal cyclizations (Ueno-Stork reaction) where the acetal center is the unique stereogenic element is reported. This highly diastereoselective reaction can be used for the preparation of polysubstituted tetrahydrofurans and gamma-lactones. We report herein the full experimental details of reactions where up to three new chiral centers are created. To demonstrate
A formalsynthesis of pseudolaric acid B, a diterpene isolated from the root bark of Pseudolarix kaempferi Gordon (Pinaceae), to Trost’s synthetic intermediate was achieved in 17 steps from a known ketone. Key features of this synthesis include a Claisen rearrangement and iodoetherification to construct quaternary stereocenters and ring-closing metathesis to form the seven-membered ring.