Asymmetric catalysis of carbonyl-ene and aldol reactions with fluoral by chiral binaphthol-derived titanium complex

2.03 Prins Reactions and Carbonyl, Imine, and Thiocarbonyl Ene Reactions

“…40 43c Mikami found that the BINOL and (i-PrO) 2 TiBr 2 or (i-PrO) 2 TiCl 2 catalyzed ene reactions with fluoral are much more successful than those with chloral. 40,41,44,45 The reaction of fluoral with methylenecyclohexane or methylenecyclopentane affords primarily ene adduct homoallylic alcohol 27 (62-79%) with much less of the allylic alcohol 28 (21-38%) (see Scheme 5). More significantly, both products are formed in 495% ee.…”

“…,41 Faller found that a (i-PrO) 2 TiCl 2 /racemic BINOL catalyst can be poisoned with an inactive enantiopure catalyst, (i-PrO) 2 TiCl 2 /diisopropyl D-tartrate to yield a catalyst that sometimes gives better ees than enantiopure BINOL 42. Thermal ene reactions of fluoral are unsuccessful.…”

Synthesis of Poly(Ethylene Glycol)–Supported (R)-BINOL Derivatives and Their First Application in Enantioselective Mukaiyama Aldol Reactions

“…[11] To the best of our knowledge, at present only a few contributions have been reported that deal with soluble PEG-supported catalysts for asymmetric Mukaiyama aldol reactions. [12] Reflecting the potential utility of the Mukaiyama process [13] in the synthesis of compounds of biological importance and based on the experience of other groups, [14][15][16][17][18][19][20][21] we have already reported an efficient method for enantioselective additions of S-ketene silyl acetal 2 to various carbonyl compounds employing a catalyst without polymer support. [22,23] In the present study, we focus our attention on the preparation of MPEG-supported BINOL ligands and their efficacy as BINOLate-titanium catalysts in enantioselective aldol reactions.…”

Highly Enantioselective Carbonyl–Ene Reactions of 2,3‐Diketoesters: Efficient and Atom‐Economical Process to Functionalized Chiral α‐Hydroxy‐β‐Ketoesters

“…The carbonyl-ene reaction is a versatile, atom-economical process for carbon-carbon bond formation. [1] Since the first asymmetric examples of this reaction reported by Yamamoto and co-workers, [2] numerous chiral Lewis [3][4][5][6][7] or Brønsted [8] acid catalytic systems have been successfully developed. With few exceptions, [4,5] glyoxylate systems have been the sole carbonyl substrates in the development of asymmetric carbonyl-ene reactions because they are highly activated, allow bidentate coordination to the catalyst, and provide access to functionalized chiral a-hydroxyacetates.…”