Highly regio- and stereoselective synthesis of (Z)-trisubstituted alkenes via propyne bromoboration and tandem Pd-catalyzed cross-coupling.
Contrary to all previous reports, bromoboration of propyne with BBr(3) proceeds in >or=98% syn-selectivity to produce (Z)-2-bromo-1-propenyldibromoborane (1). Although 1 is readily prone to stereoisomerization, it can be converted to the pinacolboronate (2) of >or=98% isomeric purity by treatment with pinacol, which may then be subjected to Negishi coupling to give trisubstituted (Z)-alkenylpinacolboronates (3) containing various R groups in 73-90% yields. Iodinolysis of 3 affords alkenyl iodides (4) in 80-90% yields. All alkenes isolated and identified are >or=98% Z.
Wang
Chao
C
Herbert C. Brown Laboratories of Chemistry, Purdue University, 560 Oval Drive, West Lafayette, Indiana 47907-2084, USA.
Tobrman
Tomas
T
Xu
Zhaoqing
Z
Negishi
Ei-ichi
E
D000475:Alkenes / Q000138:chemical synthesis* / Q000737:chemistry; D000480:Alkynes / Q000737:chemistry; D002384:Catalysis; D020650:Combinatorial Chemistry Techniques; D003432:Cross-Linking Reagents / Q000737:chemistry*; D010621:Phenazopyridine / Q000737:chemistry; D020005:Propanols / Q000737:chemistry; D013237:Stereoisomerism; D013329:Structure-Activity Relationship; D013379:Substrate Specificity
D000475:Alkenes; D000480:Alkynes; D003432:Cross-Linking Reagents; D020005:Propanols; C022030:methylacetylene; D010621:Phenazopyridine
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