Toward Multi‐Functionalized Organogermaniums: Diastereoselective Transformations of Germacycles Derived from Cheletropic Reactions of Boron‐Substituted Butadienes with Ge(II) Salts

Abstract The field of organogermanium in chemistry has recently attracted attention. Thanks to the inherent features of germanium (Ge), introducing Ge‐based substituents into organic frameworks has enhanced bioactivity and optoelectronic properties of molecules. Herein, the synthesis of multi‐functionalized organogermaniums using Ge(II) salts is reported. The germacycles having an allylboron moiety, which is derived from the (4+1) cycloadditions of the butadienes bearing a boronic ester moiety with Ge(II) salts, can be applied to further allylboration of aldehydes with perfect diastereoselectivity. The obtained allylated adducts enable access to π‐extended organogermaniums with the retention of the stereocenters.