title: Highly(≥98%) Selective Trisubstituted Alkene Synthesis of Wide Applicability via Fluoride-Promoted Pd-Catalyzed Cross-Coupling of Alkenylboranes.
abstract: (Z)-β-bromo-1-propenyl(pinacol)borane(4), recently made available in 85% yield as a ≥98% isomerically pure compound via bromoboration of 1-propyne, has been converted toβ-alkyl-, aryl-, and alkenyl-substituted (Z)-2-methyl-1-alkenyl(pinacol)boranes(2a) in ca. 75% yield based on propyne via Pd-catalyzed Negishi alkenylation with suitable organozinc bromide. The previously sluggish and modest-yielding Suzuki alkenylation ofβ,β-disubstituted alkenylboranes has been significantly promoted by fluorides, especiallynBu4NF(TBAF) or CsF to give trisubstituted alkenes, i.e., (Z)-β-Me-substituted3-i-3-xiand (E)-β-Ph-substituted2b-iand2b-ii. In all cases, each alkene product was formed in a ≥98% seteoselectivity. The propyne-based protocol nicely complements the widely used Zr-catalyzed alkyne methylalumination-Pd-catalyzed alkenylation by providing a highly stereoselective(≥98%) route to (Z)-Me-substituted alkenes.
authors: Herbert C. Brown Laboratories of Chemistry, Purdue University, 560 Oval Drive, West Lafayette, Indiana 47907-2084, USA.
authors: Ei-Ichi
authors: EI
authors: Negishi
authors: Tomas
authors: T
authors: Tobrman
authors: Honghua
authors: H
authors: Rao
authors: Shiqing
authors: S
authors: Xu
authors: Ching-Tien
authors: CT
authors: Lee
references: J Org Chem. 1996 Nov 1;61(22):7943-7946
references: 11667758
references: Chemistry. 2000 May 15;6(10):1830-3
references: 10845642
references: Angew Chem Int Ed Engl. 2007;46(16):2768-813
references: 17410611
references: Angew Chem Int Ed Engl. 2004 Apr 19;43(17):2259-63
references: 15108138
references: J Am Chem Soc. 2003 Nov 12;125(45):13636-7
references: 14599182
references: J Org Chem. 1999 Sep 3;64(18):6797-6803
references: 11674689
references: J Org Chem. 2002 Nov 29;67(24):8424-9
references: 12444620
references: Org Lett. 2009 Sep 17;11(18):4092-5
references: 19694459
references: Org Lett. 2008 Oct 2;10(19):4311-4
references: 18763786
references: Adv Synth Catal. 2010 Mar 8;352(4):627-631
references: 24072992
references: J Org Chem. 2008 Sep 5;73(17):6841-4
references: 18681402
references: Acc Chem Res. 2007 Apr;40(4):275-86
references: 17256882