All-carbon quaternary centers via ruthenium-catalyzed hydroxymethylation of 2-substituted butadienes mediated by formaldehyde: beyond hydroformylation.
Ruthenium-catalyzed transfer hydrogenation of 2-substituted dienes 1a-i in the presence of paraformaldehyde results in reductive coupling at the 2-position to furnish the hydroxymethylation products 3a-i, which embody all-carbon quaternary centers. Reductive coupling of diene 1g to paraformaldehyde under standard conditions, but employing deuterio-paraformaldehyde, 2-propanol-d(8), or both, corroborated a catalytic mechanism involving rapid, reversible diene hydrometalation with incomplete regioselectivity in advance of C-C coupling. The present method provides an alternative to the hydroformylation of conjugated dienes, for which efficient, regioselective catalytic systems remain undeveloped.
Smejkal
Tomas
T
Institut für Organische Chemie und Biochemie and Freiburg Institute for Advanced Studies (FRIAS), Albert-Ludwigs-Universität Freiburg, 79104 Freiburg, Germany.
Han
Hoon
H
Breit
Bernhard
B
Krische
Michael J
MJ
D002070:Butadienes / Q000737:chemistry*; D002244:Carbon / Q000737:chemistry*; D002384:Catalysis; D005557:Formaldehyde / Q000737:chemistry*; D006865:Hydrogenation; D007536:Isomerism; D008745:Methylation; D012428:Ruthenium / Q000737:chemistry*
D002070:Butadienes; D005557:Formaldehyde; D002244:Carbon; D012428:Ruthenium