Chiral Spirocyclic Germanium Thiolates - An Evaluation of Their Suitability for Twin Polymerization based on A Combined Experimental and Theoretical Study

Abstract

The spirocyclic germanium thiolates, 4H,4’H‐2,2’‐spirobi[benzo[d][1,3,2]dithiagermine] (1), 4H,4’H‐2,2’‐spirobi[benzo[d][1,3,2]oxathiagermine] (2) and 4H,4’H‐2,2’‐spirobi[benzo[e][1,3,2]oxathiagermine] (3) were synthesized and fully characterized. Compound 3 crystallizes as racemic conglomerate, whereas 1 and 2 give racemates in the solid state. Their reactivity towards twin polymerization (TP) was tested. The studies with regard to proton‐assisted TP revealed a significantly reduced reactivity as compared to the recently reported silicon derivative, 4H,4’H‐2,2’‐spirobi[benzo[d][1,3,2]dioxasiline] (A). DFT−D calculations were performed for 1–3 and the model compound 4H,4’H‐2,2’‐spirobi[benzo[d][1,3,2]dioxagermine] (4) to evaluate the first reaction step initiating the processes of proton‐assisted TP. Compound 4 with germanium bound to four oxygen atoms proved to be the most reactive precursor, but its synthesis failed. As indicated by the DFT−D calculations, compounds 1 and 2 are not suitable for TP. Starting from compound 3 a germanium and sulfur containing organic‐inorganic hybrid material was obtained by thermal annealing.

Construction of Ge-Stereogenic Center by Desymmetric Carbene Insertion of Dihydrogermanes

“…And germananes containing Ge–H bonds also tend to form germanium free radicals. A variety of organogermanium compounds have been synthesized and applied in organic synthesis, − catalysis, drug discovery, , and material science. − However, the enantioselective synthesis of chiral Ge-stereogenic germanes remains a challenge, with only one example reported by Nozaki, via a rhodium-catalyzed enantioselective [2 + 2 + 2] cycloaddition (Figure b). Therefore, a general synthetic method to prepare chiral germanium-stereogenic compounds is highly desired for exploring their functions.…”