19781-76-1Relevant articles and documents
TANDEM ALDOL ADDITION / ALLYL METAL ADDITION
Hoffmann, Reinhard W.,Froech, Sybille
, p. 1643 - 1646 (1985)
Addition of the enol borates 2 to aldehydes generated the internally protected aldols 3.These were subjected in situ to an allyl metal addition giving the 1,3-diols 7 or 13.This constitutes a rapid evolution of a carbon skeleton by a highly correlated tandem aldol-addition / allyl metal addition.
Ligand-controlled, norbornene-mediated, regio- and diastereoselective rhodium-catalyzed intramolecular alkene hydrosilylation reactions
Hua, Yuanda,Nguyen, Hiep H.,Scaggs, William R.,Jeon, Junha
supporting information, p. 3412 - 3415 (2013/07/26)
Ligand-controlled, norbornene-mediated, regio- and diastereoselective rhodium-catalyzed intramolecular alkene hydrosilylation of homoallyl silyl ethers (1) exploiting either BINAP or 1,6-bis(diphenylphosphino)hexane (dpph) has been developed. This method
Further studies on silatropic carbonyl ene cyclisations: β-crotyl(diphenyl)silyloxy aldehyde substrates; Synthesis of 2-deoxy-2-C-phenylhexoses
Robertson, Jeremy,Green, Stuart P.,Hall, Michael J.,Tyrrell, Andrew J.,Unsworth, William P.
experimental part, p. 2628 - 2635 (2009/02/02)
Silatropic carbonyl ene cyclisations of β-(allylsilyloxy)- and β-(crotylsilyloxy)butyraldehydes are shown to proceed with high stereoselectivity but at a much reduced rate in comparison to the cyclisation of analogous α-substrates. In the second section, olefin cross-metathesis is explored as a route to substituted α-(allylsilyloxy)aldehydes and the method applied to the synthesis of diastereomeric 2-deoxy- and 2-deoxy-2-C-phenyl hexose derivatives from butanediacetal-protected d-glyceraldehyde. The Royal Society of Chemistry 2008.
Enantioselective microbial hydrolysis of dissymmetrical cyclic carbonates with disubstitution
Nogawa, Masaki,Sugawara, Satomi,Iizuka, Rie,Shimojo, Megumi,Ohta, Hiromichi,Hatanaka, Minoru,Matsumoto, Kazutsugu
, p. 12071 - 12083 (2007/10/03)
Enantioselective microbial hydrolysis of C1 and C2 dissymmetrical cyclic carbonates with disubstitution (methyl and another groups) has been developed. Pseudomonas diminuta (FU0090), a bacterium, efficiently catalyzes the hydrolysis of five-membered cyclic carbonates. While the trans-substrates are hydrolyzed with low enantioselectivities and/or reactivities, the microbe hydrolyzes the cis-substrates with very high enantioselectivities to afford the corresponding almost optically pure anti-(2R,3S)-diols. On the other hand, six-membered trans-cyclic carbonates are enantioselectively hydrolyzed to afford the corresponding optically active syn-(2R,4R)-diols, although the hydrolysis of the cis-substrates gives racemic compounds. In all cases, the enzyme prefers the (R)-enantiomer for the carbon atom bearing a methyl group.
Diastereoselective nucleophilic substitution reactions of oxasilacyclopentane acetals: Application of the "inside attack" model for reactions of five-membered ring oxocarbenium ions
Bear, Teresa J.,Shaw, Jared T.,Woerpel
, p. 2056 - 2064 (2007/10/03)
The additions of nucleophiles to oxocarbenium ions derived from oxasilacyclopentane acetates proceeded with high diastereoselectivity in most cases. Sterically demanding nucleophiles such as the silyl enol ether of diethyl ketone add to the face opposite the C-2 substituent. These reactions establish the syn stereochemistry about the newly formed carbon-carbon bond. Small nucleophiles such as allyltrimethylsilane do not show this same stereochemical preference: they add from the same face as the substituent in C-2-substituted oxocarbenium ions. The stereoselectivities exhibited by both small and large nucleophiles can be understood by application of the "inside attack" model for five-membered ring oxocarbenium ions developed previously for tetrahydrofuran-derived cations. This stereoelectronic model requires attack of the nucleophile from the face of the cation that provides the products in their lower energy staggered conformations. Small nucleophiles add to the "inside" of the lower energy ground-state conformer of the oxocarbenium ion. In contrast sterically demanding nucleophiles add to the inside of the envelope conformer where approach is anti to the C-2 substituent of the oxocarbenium ion, regardless of the ground-state conformer population.
Addition of allylindium reagents to aldehydes substituted at Cα or Cβ with heteroatomic functional groups. Analysis of the modulation in diastereoselectivity attainable in aqueous, organic, and mixed solvent systems
Paquette, Leo A.,Mitzel, Thomas M.
, p. 1931 - 1937 (2007/10/03)
The stereochemical course of indium-promoted allylations to α- and β-oxy aldehydes has been investigated in solvents ranging from anhydrous THF to pure H2O. The free hydroxyl derivatives react with excellent diastereofacial control to give significantly heightened levels of syn-1,2-diols and anti-1,3-diols. Relative reactivities were determined in the α-series, and the hydroxy aldehyde proved to be the most reactive substrate. This reactivity ordering suggests that the selectivity stems from chelated intermediates. The rate acceleration observed in water can be heightened by initial acidification. Indeed, the indium-promoted allylation reaction mixtures become increasingly acidic on their own. Preliminary attention has been accorded to salt effects, and tetraethylammonium bromide was found to exhibit a positive synergistic effect on product distribution. Finally, mechanistic considerations are presented in order to allow for assessment of the status of these unprecedented developments at this stage of advancement of the field.
CHELATION CONTROL ASSOCIATED WITH ORGANOMETALIC ADDITION REACTION IN WATER. THE HIGH STEREOSELECTIVITY OFFERED BY α- AND β-HYDROXYL SUBSTITUENTS OBVIATES THE NEED FOR PROTECTING GROUPS.
Paquette, Leo A.,Mitzel, Thomas M.
, p. 6863 - 6866 (2007/10/02)
High stereoselectivities have been observed for indium-promoted allylations of α- and β-hydroxy aldehyes in aqueous media, with strong implication that chelate control can continue to operate in water.
STEREOSELECTIVE INTRAMOLEKULAR ALLYLSILANE ADDITIONS TO CHIRAL ALDEHYDES
Reetz, M.T.,Jung, A.,Bolm, C.
, p. 3889 - 3898 (2007/10/02)
The sense of 1,3-asymmetric induction in the TiCl4 mediated allylsilane addition of O-(allyl)silyl protected aldehydes 14 is opposite (>90percent syn selectivity) to that of the previously reported reaction of the O-benzyl protected analogs 7 with allyltrimethylsilane (>90percent anti selectivity).Crossover experiments show that strict intramolecularity pertains, suggesting an intramolecular allylsilane addition as depicted in 15.Surprisingly, the switch from TiCl4 to SnCl4 results in the reversal of diastereofacial selectivity and in an intramolecular allyl transfer mechanism. α-Chiral β-silyloxy aldehydes of the type 35 are not very well suited for stereoselective allylations.
ALLYLIC ORGANOMETALLIC WAY TO CONTROL ACYCLIC STEREOCHEMISTRY AND ITS APPLICATION TO THE SYNTHESIS OF CARBOHYDRATES
Yamamoto, Yoshinori,Komatsu, Toshiaki,Maruyama, Kazuhiro
, p. 31 - 42 (2007/10/02)
The Cram/anti-Cram selectivity in the reactions of allylmetals with aldehydes and the erythro/threo selectivity in the reactions of substituted allylic organometallic compounds with other aldehydes can be controlled by the metal (M).Based on both selectiv
