4-<i>Endo</i>-<i>T</i><i>rig</i> Cyclization Processes Using Bis(collidine)bromine(I) Hexafluorophosphate as Reagent: Preparation of 2-Oxetanones, 2-Azetidinones, and Oxetanes
作者:Fadi Homsi、Gérard Rousseau
DOI:10.1021/jo9810361
日期:1999.1.1
Reaction in methylene chloride of bis(collidine)bromine(I) hexafluorophosphate with alpha,beta-unsaturated acids and alpha,beta-unsaturated N-sulfonamides was found to lead diastereospecifically to the corresponding 2-oxetanones and 2-azetidinones in moderate yields (23-60%), by an almost unknown 4-endo cyclization. This process allow the synthesis of these interesting classes of products in one step
Ironing out the kinks: Efficientnew catalytic systems based on iron thiolates are described for the iron‐catalyzed cross‐coupling of alkyl Grignard reagents with alkenylhalides (see scheme). The reaction is highly chemo‐ and stereoselective. With this new procedure, the use of N‐methylpyrrolidone as a co‐solvent is no longer required.
A new robust methodology for gram-scale iron-catalyzed cross-coupling between alkyl Grignard reagents and alkenyl or aryl halides is developed. This method does not require toxic additives such as NMP or expensive ligands. Its efficiency relies on the use of simple alkoxide magnesium salts as additives. On the basis of these results, a new procedure for one-pot synthesis of substituted benzamides from
Cobalt-catalyzed alkenylation of organomagnesium reagents
作者:Gérard Cahiez、Hovsep Avedissian
DOI:10.1016/s0040-4039(98)01266-0
日期:1998.8
Alkenyl iodides, bromides and chlorides react with organomagnesium reagents in THF, in the presence of Co(acac)2 and NMP (9 to 4 equiv.), to give the cross-coupling products in good yields. The reaction is chemoselective (aryl or alkyl bromides, esters and ketones) and stereoselective (≥99.5%).