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Oxazolidinones hetero-Diels-Alder reaction

Ghosez and co-workers also presented a hetero-Diels-Alder reaction using a hetero-atom-containing diene 121 and the oxazolidinone 80a in the presence of bu-box 3 complexed with copper(II) triflate to afford the cycloadduct 122 in 80% yield (>99 1 exo/endo, 95% ee) as shown in Figure 9.38Z . ... [Pg.559]

In search for control of absolute stereochemistry, the reaction of thio-chalcones was investigated with unsaturated amides bearing an Evans chiral oxazolidinone [223] and dimenthyl fumarate [224, 225]. For the first time with thiocarbonyl compounds, the efficiency of Lewis acid addition was demonstrated, and reactions could be conducted at room temperature. With EtAlCl2 (Table 4, entry 2) or A1C13 (entry 3), levels of induction up to 92% were attained for the endo isomer. Yb(OTf)3 in DMSO also caused the acceleration of the reaction with chiral acrylamides with p-facial selectivity [226]. This group has also reported [227] an intramolecular hetero Diels-Alder reaction with divinyl thioketones and the double bond of an allyloxy group (Table 4, entry 4). [Pg.164]

An excellent asymmetric induction has also been observed by Snider et al. [164] in a hetero Diels-Alder reaction with the N-crotonyl oxazolidinone 2-172 which had already been used by Evans for the all carbon cycloaddition [ 164b]. Reaction of isobutene with 2-172 in the presence of Me2AlCl for 40 h at -30 °C in CH2C12 provided a mixture of the alcohol 2-174 and the lactone 2-175 via the primarily formed cycloadduct 2-173. Treatment of the mixture with sodium carbonate gave the lactone 2-175 as a pure enantiomer (Fig. 2-48). [Pg.40]

The chiral Ni(II) complex shown in Sch. 58 catalyzes the enantioselective hetero-Diels-Alder reactions of thiabutadienes with 3-(2-propenoyl)-2-oxazolidinone to afford optically active dihydrothiopyrans [204]. Similar results are obtained with analogous Cu(II) complexes where catalyst loading can be reduced when molecular sieves are added. [Pg.643]

Hetero-Diels-Alder reaction. The condensation of conjugated a-ketoesters with A -alkenyl-2-oxazolidinones shows facial stereodivergence due to the presence of different Lewis acids. For example, stereoisomers are obtained from reactions catalyzed by SnCU and by Eu(fod)3. ... [Pg.436]

Hetero Diels-Alder reactions of l-thia-3-aza-l,3-butadienes with chiral a,p-unsaturated oxazolidinones in the presence of MgBr2 at O C yield 1,3-thiazines diastereoselectively in high yield. [Pg.106]

The initial work on the asymmetric [4-1-2] cycloaddition reactions of A -sulfinyl compounds and dienes was performed with chiral titanium catalysts, but low ee s were observed <2002TA2407, 2001TA2937, 2000TL3743>. A great improvement in the enantioselectivity for the reaction of AT-sulfinyl dienophiles 249 or 250 and acyclic diene 251 or 1,3-cyclohexadiene 252 was observed in the processes involving catalysis with Cu(ll) and Zn(ii) complexes of Evans bis(oxazolidinone) (BOX) ligands 253 and 254 <2004JOC7198> (Scheme 34). While the preparation of enantio-merically enriched hetero-Diels-Alder adduct 255 requires a stoichometric amount of chiral Lewis acid complex, a catalytic asymmetric synthesis of 44 is achieved upon the addition of TMSOTf. [Pg.552]

An extensive review of recent advances in the area of asymmetric Diels-Alder reactions has been published.205 Sterically constrained tricyclic 2-oxazolidinones serve as excellent chiral auxiliaries for asymmetric Diels-Alder reactions.206 The Diels-Alder reactions of ( —)-(a,S. 7,S )-colchicinc (109) with hetero- and carbo-dienophiles show... [Pg.452]

Section 1.1.3.3 Formation of 1-vinyl-2-alkylcyclohexanes from 1,7-dienes. Narasaka demonstrated that the chiral titanium alkoxide prepared from TiCl2(OPr )2 and (213) catalyzes the asynunetric intramolecular ene reaction of oxazolidinone (212) in Freon 113 at 0 °C to give 63% of ene adduct (214) in >98% enantiomeric excess and 25% of the hetero Diels-Alder adduct. ... [Pg.25]


See other pages where Oxazolidinones hetero-Diels-Alder reaction is mentioned: [Pg.126]    [Pg.407]    [Pg.418]    [Pg.455]    [Pg.455]    [Pg.79]    [Pg.29]    [Pg.420]    [Pg.455]    [Pg.722]   
See also in sourсe #XX -- [ Pg.559 ]




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Hetero-Diels-Alder

Hetero-Diels-Alder reaction

Oxazolidinone

Oxazolidinone reactions

Oxazolidinones

Oxazolidinones Diels-Alder reaction

Oxazolidinones, reactions

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