radical germylzincation of -heteroatom ......radical germylzincation of a-heteroatom-substituted...
TRANSCRIPT
RADICAL GERMYLZINCATION OF a-HETEROATOM-SUBSTITUTED ALKYNES
Karen DE LA VEGA-HERNANDEZ,a Elise ROMAIN,a Anais COFFINET,a Kajetan BIJOUARD,a Geoffrey GONTARD,a Fabrice CHEMLA,a Franck FERREIRA,a
Olivier JACKOWSKIa and Alejandro PEREZ-LUNAa
a Sorbonne Université, CNRS, Institut Parisien de Chimie Moléculaire, 4 place Jussieu, 75005 Paris, France
Vinylgermanes are interesting synthetic building blocks that provide specific features such as low toxicity, facilehalodegermylation and excellent stability toward protonolysis. With a reactivity pattern similar to that of vinylsilanes andvinylstannanes, vinylgermanes offer a useful alternative to the more popular group 14 homologues when they meet flaws.[2]
However, there is no direct synthetic method for the preparation of β,β’-polysubstituted vinylgermanes.
Alkyne germylmetalation,[3] i. e., the 1,2-addition of germanium‒metal bonds across the carbon-carbon triple bond of alkynes, isa conceptually appealing approach for the synthesis of β-metalated vinylgermanes that could be used for the synthesis of tri- andtetrasubstituted vinylgermanes after in situ functionalization of the C(sp2)‒Met bond.
We disclosed here the first germylzincation reaction of C‒C triple bonds using a combination of a hydrogermane anddiethylzinc in a radical chain process. This reaction selectively installs a C(sp2)‒Ge bond and a C(sp2)‒Zn bond, that can be used aslinchpin for subsequent functionalization in a one pot procedure, offering modular access to tailored vinylgermanes that are not
achievable by other methods.
GERMYLZINCATION OF a-HETEROATOM-SUBSTITUTED ALKYNES[1]
REACTION SCOPE C(sp2)‒Zn BOND FUNCTIONALIZATION
Isolated after column chromatography on silica gel!
C(sp2)‒Ge BOND FUNCTIONALIZATION
MECHANISMt1
(min)
TEMPO
(mol%)2/1
0 110 0:100
0 10 0:100
5 10 26:74
REFERENCES ACKNOWLEDGMENTS
Sorbonne Université / CNRS / ED 406 are acknowledged for financial support.
[1] de la Vega-Hernández, K; Romain, E; Coffinet, A; Bijouard, K; Gontard, G; Chemla, F; Ferreira, F; Jackowski, O; Perez-Luna, A. J. Am. Chem. Soc. 2018, 140, 17632-17642.[2] (a) Oda, H; Morizawa, Y; Oshima, K; Nozaki, H. Tetrahedron Lett. 1984, 25, 3221-3224. (b) Tresse, C; Schweizer, S; Bisseret, P; Lalevée, J; Evano, G; Blanchard, N. Synthesis 2016, 48, 3317-3330.[3] (a) Oda, H.; Morizawa, Y.; Oshima, K.; Nozaki, H. Tetrahedron Lett. 1984, 25, 3217–3220. (b) Piers, E.; Lemieux, M. Organometallics 1998, 17, 4213–4217.
StereoselectivityModel