(R)- and (S)-4-TIPS-3-butyn-2-ol. Useful precursors of chiral allenylzinc and indium reagents.
A convenient route to the enantiomers of 4-TIPS-3-butyn-2-ol of >95% enantiomeric purity by reduction of the ynone precursor 4 with the Noyori N-tosyl-1,2-diphenylethylenediamineruthenium cymene catalyst is described. The mesylate derivative of the (S) enantiomer (1c) is converted in situ to an allenylzinc or indium reagent in the presence of a catalyst derived from Pd(OAc)2 and Ph3P and either Et2Zn or InI. A second in situ addition of these reagents to aldehydes leads to anti homopropargylic alcohol adducts. The additions proceed in generally high (60-90%) yield with modest to excellent diastereoselectivity and high enantioselectivity. Only slight mismatching (<5%) is observed with chiral alpha-methyl and alpha-silyloxy aldehydes. Additions to alpha-substituted enals are highly diastereoselective, while beta,beta-disubstituted enals afford ca. 2:1 mixtures of anti and syn adducts.
Marshall
James A
JA
Department of Chemistry, University of Virginia, McCormick Road, P.O. Box 400319, Charlottesville, Virginia 22904-4319, USA. jam5x@virginia.edu
Eidam
Patrick
P
Eidam
Hilary Schenck
HS
D000466:Alkadienes / Q000737:chemistry; D000440:Butanols / Q000138:chemical synthesis* / Q000737:chemistry; D002384:Catalysis; D007204:Indium / Q000737:chemistry*; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry*; D012428:Ruthenium / Q000737:chemistry*; D012821:Silanes / Q000138:chemical synthesis* / Q000737:chemistry; D013237:Stereoisomerism; D015032:Zinc / Q000737:chemistry*
C520519:4-TIPS-3-butyn-2-ol; D000466:Alkadienes; D000440:Butanols; D009942:Organometallic Compounds; D012821:Silanes; D007204:Indium; D012428:Ruthenium; D015032:Zinc