- Chiral diphosphorus compounds and transition metal complexes thereof
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The present invention relates to chiral diphosphorus compounds and transition metal complexes thereof, to a process for preparing chiral diphosphorus compounds and oxides thereof, and transition metal complexes comprising the chiral diphosphorus compounds. In a further aspect, the invention relates to the use of the chiral diphosphorus compounds or transition metal complexes thereof in asymmetric syntheses.
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Page/Page column 7
(2008/06/13)
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- Chiral diphosphorus compounds and their transition metal complexes
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Chiral diphosphorus compounds (I) and their complexes with boranes are new. Chiral diphosphorus compounds of formula (I) and their complexes with boranes are new. *1-*3 : stereogenic C atom in R- or S- configuration; R 5>alkyl, arylalkyl or aryl; either R 1>-R 4>R 5> or 4-16C heterocyclic group; or R 1>+R 2> and/or R 3>+R 4>alkylene; R 6>R 5> or alkoxy; and n : 0-2. Independent claims are also included for the following: (1) phosphorus-containing cyclopentanol compounds of formula (IV); (2) phosphorus containing cyclopentane derivatives of formula (V) and (VI); (3) phosphorus containing cyclopentanol compounds of formula (VII) and their complexes with borane; (4) sulfur-containing cyclopentanol compounds of formula (IX); (5) the preparations of (I), (IV), (V), (VI), (VII) and (IX); (6) cyclopentanol compounds of formula (II); (7) transition metal complexes (C1) comprising (I); (8) catalysts (C2) comprising (C1); and (9) a method for preparing stereoisomerically enriched compounds in the presence of (C2). [Image] [Image].
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Page/Page column 12
(2008/06/13)
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- Reactions of tin(IV) enolates obtained from O-stannyl ketyls under neutral free radical conditions
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Under mild and neutral free radical conditions, an α,β-unsaturated ketone reacted with tributyltin hydride to produce an intermediate resonance-stabilized allylic O-stannyl ketyl. Upon subsequent hydrogen atom abstraction, a tin(IV) enolate was afforded which could be quenched with a variety of electrophiles and form new carbon-carbon bonds. Aldehydes react to produce aldol-type products and both intramolecular and intermolecular carbonyl addition reactions were investigated using this strategy. Using similar methodology, the tin(IV) enolate could be quenched in the presence of HMPA with various alkyl halides and α,β-unsaturated carbonyl compounds (Michael acceptors) to yield alkylated products in good yields. These reactions represent a very mild regioselective alternative to metal enolate formation which usually requires strong bases such as LDA or strongly reductive dissolving metal conditions to achieve success. New carbon skeletons for natural product synthesis can be readily constructed using this chemically neutral approach.
- Enholm, Eric J.,Whitley, Paul E.,Xie, Yongping
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p. 5384 - 5390
(2007/10/03)
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- INTERMOLECULAR ALDOL REACTIONS VIA ALLYLIC O-STANNYL KETYLS
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A mild and neutral free radical reaction of an α,β-unsaturated ketone and tributyltin radical produced a resonance-stabilized allylic O-stannyl ketyl intermediate.A tin(IV)enolate, produced by subsequent hydrogen atom transver, was next quenched with various aldehydes to yield an aldol product which was readily eliminated with p-toluenesulfonic acid to afford new α,β-unsaturated ketones with E/Z ratios up to > 100:1.
- Enholm, Eric J.,Whitley, Paul E.
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p. 9157 - 9160
(2007/10/02)
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