Diastereoselective conjugate additions to pi-allylmolybdenum complexes: a stereocontrolled route to 3,4,5-trisubstituted gamma-butyrolactones.
[reaction: see text] pi-Allylmolybdenum complex 6b is obtained as a single isomer by Knoevenagel condensation of aldehyde 1 with Meldrum's acid. Conjugate additions of Grignard reagents to Meldrum's acid alkylidene derivative 6b are shown to be completely diastereoselective. Further functional group transformation of the 1,4-adducts, followed by demetalation, leads to trisubstituted tetrahydrofurans and gamma-butyrolactones. Whereas the synthesis of tetrahydrofurans (X = 2H) is not completely stereoselective, the gamma-butyrolactones (X = O) are obtained with good to excellent diastereoselectivities.
Pearson
Anthony J
AJ
Department of Chemistry, Case Western Reserve University, Cleveland, Ohio 44106, USA. ajp4@po.cwru.edu
Mesaros
Eugen F
EF
D015107:4-Butyrolactone / Q000138:chemical synthesis*; D008982:Molybdenum / Q000737:chemistry*; D013237:Stereoisomerism
D008982:Molybdenum; D015107:4-Butyrolactone