Thiopyran route to polypropionates: exploiting and overcoming double stereodifferentiation and mutual kinetic enantioselection in aldol couplings of chiral fragments.
The aldol reaction of tetrahydro-4H-thiopyranone with 1,4-dioxa-8-thiaspiro[4.5]decane-6-carboxaldehyde (I) gives four possible diastereomeric adducts (II). Aldol reactions of I with each of the diastereomers of II and their corresponding methoxymethyl ethers III via the Ti enolates were investigated. Using racemic reactants, reactions with II proceeded with high levels of mutual kinetic enantioselection (MKE) and double stereodifferentiation (DS) to give one of the eight possible bisaldol adducts. Similar reactions of III proceeded with low levels of MKE and DS and gave two bisaldol adducts, one from each of the possible combinations of enantiomeric reactants. By extension, 11 of the 20 possible diastereomers of the bisaldol adduct could be obtained selectively. These adducts are useful for polypropionate synthesis.
Ward
Dale E
DE
Department of Chemistry, University of Saskatchewan, 110 Science Place, Saskatoon SK S7N 5C9, Canada. dale.ward@usask.ca
Beye
Garrison E
GE
Sales
Marcelo
M
Alarcon
Idralyn Q
IQ
Gillis
H Martin
HM
Jheengut
Vishal
V
D000447:Aldehydes / Q000138:chemical synthesis*; D002384:Catalysis; D002855:Chromatography, Thin Layer; D007202:Indicators and Reagents; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D008968:Molecular Conformation; D011714:Pyrans / Q000138:chemical synthesis*; D013141:Spiro Compounds / Q000138:chemical synthesis*; D013237:Stereoisomerism
D000447:Aldehydes; D007202:Indicators and Reagents; D011714:Pyrans; D013141:Spiro Compounds