Stannyl formylation

The formylation of metalated sp carbons, for example in a stannylbenzene (Eq. 185) [458] or in vinylsilanes [459,460] (Eq. 186), with Cl2CH(OMe) and TiCU, in which the ipso carbon to the stannyl or silyl group is selectively formylated, has been reported. The formylation of a vinylsilane was used in the preparation of a terpene aldehyde, nuciferal, as shown in Eq. (186) [461]. 

Acetone cyanhydrin and aluminium chloride may be used in place of hydrogen cyanide in the Gattermann formylation of aromatic compounds. Yields and substrate reactivities are comparable to those observed with the Gattermann procedure. The trimethylstannyl groups in stannyl-pyridines and -quinolines may be replaced regiospecifically by acyl groups by reaction with acyl chlorides. When the tin substituent is not at the 2-position, palladium catalysis is necessary, but this also leads to a small amount of formation of a bipyridyl [equation (10)1. 

---