Direct, Sequential, and Stereoselective Alkynylation of C,C-Dibromophosphaalkenes.
The first direct alkynylation of C,C-dibromophosphaalkenes by a reaction with sulfonylacetylenes is reported. Alkynylation proceeds selectively in the trans position relative to the P substituent to afford bromoethynylphosphaalkenes. Owing to the absence of transition metals in the procedure, the previously observed conversion of dibromophosphaalkenes into phosphaalkynes through the phosphorus analog of the Fritsch-Buttenberg-Wiechell rearrangement is thus suppressed. The bromoethynylphosphaalkenes can subsequently be converted to C,C-diacetylenic, cross-conjugated phosphaalkenes by following a Sonogashira coupling protocol in good overall yields. By using the newly described method, full control over the stereochemistry at the P=C double bond is achieved. The substrate scope of this reaction is demonstrated for different dibromophosphaalkenes as well as different sulfonylacetylenes.
Department of Chemistry - Ångström Laboratories, Molecular Inorganic Chemistry, Uppsala University, Box 523, 75120, Uppsala, Sweden.
Muhammad A
MA
Shameem
Department of Chemistry - Ångström Laboratories, Molecular Inorganic Chemistry, Uppsala University, Box 523, 75120, Uppsala, Sweden.
Keyhan
K
Esfandiarfard
Department of Chemistry - Ångström Laboratories, Molecular Inorganic Chemistry, Uppsala University, Box 523, 75120, Uppsala, Sweden.
Elisabet
http://orcid.org/0000-0002-0104-3163
E
Öberg
Department of Chemistry - Ångström Laboratories, Molecular Inorganic Chemistry, Uppsala University, Box 523, 75120, Uppsala, Sweden. sascha.ott@kemi.uu.se.
Sascha
S
Ott
Department of Chemistry - Ångström Laboratories, Molecular Inorganic Chemistry, Uppsala University, Box 523, 75120, Uppsala, Sweden. andreas.orthaber@kemi.uu.se.
Andreas
http://orcid.org/0000-0001-5403-9902
A
Orthaber
Sonogashira coupling; alkynylation; cross-conjugation; phosphaalkenes; sulfonyl coupling