Ligandless Iron‐Catalyzed Desulfinylative C–C Allylation Reactions using Grignard Reagents and Alk‐2‐enesulfonyl Chlorides

Alk‐2‐enesulfonyl chlorides 1–4 were synthesized by the BCl3‐promoted ene reaction of alkenes with SO2. These sulfonyl chlorides were then used as electrophilic partners in iron‐catalyzed desulfinylative cross‐coupling reactions with different Grignard reagents (aromatic, aliphatic, andheteroaromatic). The reaction can be catalyzed with even 2 mol‐% of the simple iron salt Fe(acac)3. The regioselectivity of these allylations was studied by using sulfonyl chlorides 3 and 4 with aryl Grignard reagents. The scope of these allylations was further extended by the coupling of ester‐substituted alk‐2‐enesulfonyl chloride 10 with aromatic Grignard reagents. Symmetrical products were synthesized by double C–C allylation with the use of 2‐methylidenepropane‐1,3‐disulfonyl chloride (12). (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)