- Regio- And stereoselective synthesis of alkyl allylic ethers via gold(l)-catalyzed intermodular hydroalkoxylation of allenes with alcohols
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Reaction of 1-phenyl-1,2-butadiene with 2-phenyl-1-ethanol catalyzed by a 1:1 mixture of a gold(l) W-heterocyclic carbene complex and AgOTf at room temperature for 1 h led to isolation of (E)-(3-phenethoxy-1-butenyl)benzene in 96% yield as a single regio-
- Zhang, Zhibin,Widenhoefer, Ross A.
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supporting information; scheme or table
p. 2079 - 2081
(2009/04/10)
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- A highly stereoselective ether directed palladium catalysed aza-Claisen rearrangement
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A highly stereoselective rearrangement of allylic trichloroacetimidates to allylic trichloroamides has been achieved using adjacent ether groups to direct facial coordination of the palladium(II) catalyst. The Royal Society of Chemistry 2005.
- Jamieson, Andrew G.,Sutherland, Andrew
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p. 735 - 736
(2007/10/03)
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- Flexible and simple route for the stereoselective synthesis of trisubstituted γ-butyrolactones: Total synthesis of (+)-blastomycinone and its analogs
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A flexible route for the stereoselective synthesis of trisubstituted γ-butyrolactones, namely (+)-blastomycinone and its analogs, is devised by the Sharpless asymmetric epoxidation and the regioselective ring opening reaction with dibutylcopper lithium as
- Krishna, Palakodety Radha,Reddy, V. V. Ramana,Sharma
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p. 2107 - 2114
(2007/10/03)
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- Diastereoselective synthesis of enantiopure 5-[2-(alkoxyalkyl)-1- (hydroperoxypropyl)]-3-alkoxycarbonyl-2-alkyl furans
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The diastereoselective approach to enantiomerically pure furyl hydroperoxides of general type 1 has been accomplished starting from (S)-(- )-ethyl lactate. In the first part of the synthesis the alkylating reagents 7a,b were efficiently produced to be use
- Lattanzi, Alessandra,Sagulo, Francesco,Scettri, Arrigo
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p. 2023 - 2035
(2007/10/03)
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- "Chirality transfer" in iron-mediated dienylic substitutions via highly enantiomerically enriched planar chiral 1-phenylsulfonyl-substituted tricarbonyl(η5-pentadienyl)iron(1 +) complexes
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The preparation of highly diastereo-and enantiomerically enriched planar chiral 1-phenylsulfonyl-substituted tricarbonyl(η5-pentadienyl)iron(1 +) complexes 7 [syn,syn-(1R,5R)-7 and syn,syn-(1S,5S)-7 (cisoid-or U-forms); de > 99% ≡ 5-syn-CH3/5-anti-CH3 ? 100:1, ee > 99%; 87% quant. from resolved 6] is described. Starting from the enantiopure diene (1E,3E,S)-5 both enantiomers of the cationic complexes syn,syn-7 become readily accessible via chromatographic resolution of the diastereomeric mixture of the corresponding neutral tricarbonyl(η4-diene)iron(0) complexes 6 [(1R,5S)-6 ≡ ψ-endo-6 and (1S,5S)-6 ≡ ψ-exo-6; de > 99%, ee > 99%; 85% quant. prior to resolution]. The nucleophilic addition of hetero and carbon atom nucleophiles (morpholine, silyl enol ether 8 and silyl ketene acetal 9) to the racemic complex syn,syn-(1R/S,5R/S)-7 afforded the neutral ε-substituted tricarbonyl(η4-diene)iron(0) complexes rac-ψ-exo-10a-c in moderate yields [43-68% from syn,syn-(1R/S,5R/S)-7] as single geometrical isomers [(E,Z) or (E,E); kinetic (U-form/strong nucleophile) or thermodynamic (S-form/less reactive nucleophile) control]. Likewise, nucleophilic addition to the stereochemically homogeneous complexes syn,syn-(1R,5R)-7 or syn,syn-(1S,5S)-7 followed by oxidative cleavage of the carbonyliron fragment offers an access to ε-substituted dienes 11a-c in moderate to fair yields [45-65%, (E,Z)/(E,E) = > 85:1-1:3] with enantiomeric excesses ranging from > 99%/98.9% [(1E,3Z,R)-11a/(1E,3Z,S)-11a] to 93% [(6E,8E,S)-11b]. The stereochemistry of the formation and the stereochemical pathways of the nucleophilic addition reactions of the nonracemic complexes syn,syn-7 leading to the dienes 11a-c as well as spectroscopic and structural details are discussed. Furthermore, the reaction proceeds with virtually complete "chirality transfer" from C-O via C-Fe to C-N or C-C, respectively, with either retention or inversion of stereochemistry of the stereogenic centre with respect to the starting material (S)-1 depending strongly on the reaction conditions. The observed ε-regioselectivity of the nucleophilic addition reaction displays the synthetic equivalence of the cationic complexes of type syn,syn-7 with a planar chiral a6-synthon allowing an umpolung of the classical d6-chemistry.
- Enders, Dieter,Jandeleit, Bernd,Von Berg, Stefan
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p. 219 - 236
(2007/10/03)
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- Diastereoselectivity of the thio-Claisen rearrangement of acyclic precursors bearing a chiral centre adjacent to carbon 6
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A number of chiral allylic alcohols have been prepared and submitted to a Mitsunobu reaction with dithioacetic acid. Allyl dithioesters were deprotonated by LDA at -30°C and resulting enethiolates were quenched with iodomethane to afford quantitatively S-
- Desert, Stephane,Metzner, Patrick
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p. 10327 - 10338
(2007/10/02)
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- Stereoselective Intramolecular Nitrone Cycloadditions Promoted by an Allylic Stereocenter
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A series of intramolecular nitrone cycloadditions to chiral allyl ethers was studied in order to evaluate the influence on the stereochemical outcome exerted by several factors, including the nature of the substituents at the stereocenter and the steric and electronic features of the double bond.A comparison between the stereoselectivity of these reactions and that of related nitrile oxides cycloadditions suggests that they could proceed via similar transition states.
- Annunziata, Rita,Cinquini, Mauro,Cozzi, Franco,Raimondi, Laura
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p. 1901 - 1908
(2007/10/02)
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- AN OBSERVATION OF DIASTEREOFACE SELECTIVITY IN THERMAL REACTIONS BETWEEN δ-ALKOXYALLYLSTANNANES AND ALDEHYDES
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The δ-alkoxyallylstannanes (4) and (5) react stereoselectively on heating with p-nitrobenzaldehyde to provide the homoallylic alcohols (14) - (17), with (14) : (15) = 82 : 18; (16) : (17) = 73 : 27
- Mortlock, Simon V.,Thomas, Eric J.
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p. 2479 - 2482
(2007/10/02)
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- INTRAMOLECULAR NITRILE OXIDE CYCLOADDITION ON CHIRAL OLEFINS : A STEREOCONTROLLED APPROACH TO β-KETOL PRECURSORS.
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The intramolecular nitrile oxide cycloaddition reaction on (E) or (Z) olefins featuring a sulphur atom along the carbon chain connecting dipole and dipolarophile occurs with a poor to excellent anti stereoselectivity, which is mainly affected by the subst
- Annunziata, Rita,Cinquini, Mauro,Cozzi, Franco,Dondio, Gulio,Raimondi, Laura
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p. 2369 - 2380
(2007/10/02)
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- Further studies on stereospecific epoxidation of allylic alcohols Iltifat Hasan
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A stereosepcific synthesis of the epoxides 4 and 12c is described.
- Hasan, Iltifat,Kishi, Yoshito
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p. 4229 - 4232
(2007/10/02)
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