Iron-mediated preparation of vinylcyclopropanecarboxylates: scope, mechanism, and applications.
The addition of stabilized carbon nucleophiles to tricarbonyl(1-methoxycarbonylpentadienyl)iron(1+) cation (1a) proceeds via attack at C2 on the face of the ligand opposite the Fe(CO)(3) group to generate tricarbonyl(pentenediyl)iron complexes 2. Oxidation of complexes 2 affords vinylcyclopropanecarboxylates in good yield. In general, the relative stereochemistry about the cyclopropane ring reflects reductive elimination with retention of configuration. In cases where the C2 substituent is bulky (i.e., 2b) the major cyclopropane product 9b represents ring closure with inversion at C3. A mechanism involving pi-sigma-pi rearrangement of the initially oxidized (pentenediyl)iron species is proposed to account for these results. Experiments which probe the stereochemistry of deuterium labeling in the vinyl group of the vinylcyclopropanecarboxylate products were carried out, and these results are consistent with the proposed mechanism. This methodology for the preparation of vinylcyclopropanecarboxylates was applied to the synthesis of 2-(2'-carboxycyclopropyl)glycines (+)-22 and (-)-23 and the cyclopropane triester (-)-26.
Yun
Young K
YK
Department of Chemistry, Marquette University, Milwaukee, Wisconsin 53201-1881, USA.
Godula
Kamil
K
Cao
Yeyu
Y
Donaldson
William A
WA
D002264:Carboxylic Acids / Q000138:chemical synthesis*; D002384:Catalysis; D002625:Chemistry, Organic / Q000379:methods*; D003500:Cyclization; D003521:Cyclopropanes / Q000138:chemical synthesis*; D003903:Deuterium / Q000737:chemistry; D005998:Glycine / Q000031:analogs & derivatives* / Q000138:chemical synthesis*; D007501:Iron / Q000737:chemistry*; D008024:Ligands; D008968:Molecular Conformation; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis*; D010084:Oxidation-Reduction; D013237:Stereoisomerism; D014753:Vinyl Compounds / Q000138:chemical synthesis*
D002264:Carboxylic Acids; D003521:Cyclopropanes; D008024:Ligands; D009942:Organometallic Compounds; D014753:Vinyl Compounds; D003903:Deuterium; D007501:Iron; D005998:Glycine