Site‐Selective Pd‐Catalysed Fujiwara‐Moritani type Reaction of N,S‐Heterocyclic Systems with Olefins

Dihydro‐1,4‐thiazine skeletons bearing olefin fragment at their α‐position were prepared through a Pd(OAc)2‐catalysed Fujiwara‐Moritani type reaction via C−H alkenylation with olefins. This approach is selective, generalizable to a wide range of olefins and requires only 1 eq. of Ag2CO3 without the need of co‐oxidant. The C−H bond activation proved to be strongly dependent on the olefin's substitution while unfused dihydro‐1,4‐thiazines seemed to be affected by the oxidation state of the sulfur atom. The utility of olefins obtained was demonstrated by their implication in the dipolar cycloaddition reaction with a non‐stabilized azomethine ylide.