Steric bulk around catalytic centers is one of the most important factors determining catalytic reactivities and selectivities. This paper reports the synthesis of structurally diverse 5-iodo-3-methyl-1,2,3-triazolium salts and the evaluation of their catalytic activities as halogen-bonding donors for the aza-Diels-Alder reaction of 2-siloxy-1,3-butadiene with imines. We found that steric hindrance around an iodide atom in halogen-bonding donors significantly impacted catalytic efficiency.

The first example of palladium-catalyzed direct formylation of arylzinc reagents using S-phenyl thioformate is reported. The reaction proceeded under mild conditions, allowing high functional group tolerance. In addition, the developed formylation method was used to prepare deuterated and C-labeled aryl aldehydes from isotope-labeled S-phenyl thioformates. Moreover, this procedure was applied to an alkenylzinc halide, affording the corresponding enal.

We report the synthesis of enal compounds by palladium‐catalyzed formylation of alkenylzinc reagents with S‐(4‐nitrophenyl) thioformate. Various functional groups were tolerated in the present reaction. 1H NMR experiments revealed that the products had a non‐protected formyl group, which can be utilized for further C–C bond formation reactions. We successfully achieved the one‐pot synthesis of a 1,5‐diene‐3‐ol compound via sequential formylation and allylation.