Highly selective synthesis of (E)-3-methyl-1-trialkylsilyl-3-en-1-ynes via trans-selective alkynylation catalyzed by Cl2Pd(DPEphos) and stereospecific methylation with methylzincs catalyzed by Pd(tBu3P)2.
[reaction: see text] trans-Selective (>or=98%) monoalkynylation of 1,1-dibromo-1-alkenes and 1,1-dichloro-1-alkenes catalyzed by Cl(2)Pd(DPEphos) followed by stereospecific methylation with Me(2)Zn or MeZnX (X= Cl or Br) catalyzed by Pd((t)()Bu(3)P)(2) provides an efficient and stereoselective (>or=98%) route to 5, convertible to a wide variety of enynes and conjugated dienes. In the cases of 1,1-dibromo-1-alkenes, the Sonogashira alkynylation may also be satisfactory, but it is distinctly less satisfactory than the alkynylzinc reaction in cases where 1,1-dichloro-1-alkenes are used.
Shi
Ji-Cheng
JC
Herbert C. Brown Laboratories of Chemistry, Purdue University, West Lafayette, Indiana 47907-2084, USA.
Zeng
Xingzhong
X
Negishi
Ei-Ichi
E
D000480:Alkynes / Q000138:chemical synthesis*; D002384:Catalysis; D007202:Indicators and Reagents; D008745:Methylation; D009942:Organometallic Compounds / Q000737:chemistry; D010165:Palladium / Q000737:chemistry; D012821:Silanes / Q000138:chemical synthesis*; D013237:Stereoisomerism
D000480:Alkynes; D007202:Indicators and Reagents; D009942:Organometallic Compounds; D012821:Silanes; D010165:Palladium