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1.
Aldol reaction of enones 1a-c with aldehydes followed by intramolecular conjugate addition proceeded smoothly to afford corresponding 2,3-dihydro-4H-pyran-4-ones in high yields under mild conditions. 相似文献
2.
Radical addition of aldehydes and masked aldehydes like 1,3-dioxolanes to electron-deficient alkenes was achieved by the use of catalytic amounts of BPO and N-hydroxyphthalimide (NHPI) as a polarity-reversal catalyst under mild conditions. Three-component radical coupling of 1,3-dioxolanes, maleates, and alkenes was performed in the presence of BPO and NHPI under similar conditions. 相似文献
3.
Lu Chang 《Tetrahedron letters》2008,49(47):6663-6666
The enantioselective oxa-Michael addition reaction of 1-(4-methoxyphenyl) ethanone oxime to various α,β-unsaturated aldehydes was accomplished by using chiral N,N′-dioxide-FeSO4·7H2O (1:1) complex. Aromatic acid was employed as additive to increase the yield of the reaction. The corresponding adducts were obtained in moderate yields with up to 76% ee under mild conditions. 相似文献
4.
Jade Vaccari María Jos Gonzlez-Soria Nicholas Carter Beatriz Maci 《Molecules (Basel, Switzerland)》2021,26(15)
A catalytic methodology for the enantioselective addition of alkylzirconium reagents to aliphatic aldehydes is reported here. The versatile and readily accessible chiral Ph-BINMOL ligand, in the presence of Ti(OiPr)4 and a zinc salt, facilitates the reaction, which proceeds under mild conditions and is compatible with functionalized nucleophiles. The alkylzirconium reagents are conveniently generated in situ by hydrozirconation of alkenes with the Schwartz reagent. This work is a continuation of our previous work on aromatic aldehydes. 相似文献
5.
Some novel functionalized indeno[1,2-b]furans were synthesized from the reaction of indandione/indanone and aldehydes at room temperature followed by the reaction of the Knoevenagel condendensed intermediate with 4-hydroxycoumarins in the presence of iodine as catalyst in dimethyl sulfoxide (DMSO) under thermal conditions. The reaction involved in a condensation and Michael addition followed by lactone ring opening and intramolecular cyclization process to afford the product in high yield in easy work-up procedure. 相似文献
6.
Mustafa Catir Murat Cakici Semistan Karabuga Sabri Ulukanli Ertan Şahin Hamdullah Kilic 《Tetrahedron: Asymmetry》2009,20(24):2845-2853
Optically active propargylic alcohols are important chiral-building blocks in asymmetric synthesis, while the asymmetric addition of a terminal alkyne to an aldehyde is one of the most important procedures to prepare these chiral-building blocks. In this work, a family of chiral 4,4′-biquinazoline alcohols has been conveniently prepared from the easily accessible (S)-2-acetoxycarboxylic acid chlorides by reaction sequences beginning with condensation and followed by key synthetic steps including chlorination, nickel(0)-mediated homocoupling, and deprotection in addition to being examined as potential ligands in the enantioselective addition of phenylacetylene to aldehydes. These chiral ligands can be combined with Ti(OiPr)4 and then used to catalyze the asymmetric addition of zinc acetylide, produced in situ by the reaction of phenylacetylene with diethylzinc, to aldehydes. The best enantiomeric excess obtained in this study was 75%. 相似文献
7.
An efficient and regioselective synthesis of functionalized benzenes via the cascade reactions of 1,2-allenic ketones with 4-sulfonyl crotonates under mild reaction conditions has been established. Mechanistically, the formation of the title compounds involves a cascade procedure consisting of an intermolecular regioselective Michael addition followed by an intramolecular condensation and aromatization. Compared with those of α,β-unsaturated aldehydes/ketones, the reactions of 1,2-allenic ketones with 4-sulfonyl crotonates demonstrated contrary regio-selectivity and distinct reaction conditions. Moreover, the functionalized benzene products obtained herein were found to be ready intermediates for the synthesis of fluorenone and anthracenone derivatives. 相似文献
8.
Shaohua Gou 《Tetrahedron letters》2009,50(3):281-283
Enantioselective addition of diethylzinc to a series of aromatic aldehydes is developed using new chiral C2-symmetric ligand (S)-2,2′-(1,1′-binaphthyl-2,2′-diylbis(oxy))bis(methylene)bis(4-nitrophenol) (S)-2b. The catalytic system employing 10 mol % of (S)-2b and 120 mol % of Ti(OiPr)4 was found to promote the addition of diethylzinc to a wide range of aromatic aldehydes with electron-donating and electron-withdrawing substituents, giving up to 89% ee and up to 95% yield of the corresponding secondary alcohol under mild conditions. 相似文献
9.
Aldimines (generated in situ from aldehydes and amines) undergo ready addition with ethyl diazoacetate in the presence of a catalytic amount of lithium perchlorate in acetonitrile to afford the corresponding cis-aziridine carboxylates in high yields with high diastereoselectivity. 10 mol% LiClO4 in acetonitrile provides a convenient catalytic media to perform the reactions under mild and neutral conditions. 相似文献
10.
《Tetrahedron: Asymmetry》2014,25(24):1599-1604
Two chiral aromatic l-prolinamides were synthesized in high overall yield (95%) from N-Boc-l-proline and served as organocatalysts in asymmetric Michael reactions of aldehydes to nitroalkenes. Under the optimized reaction conditions, (S)-N-tritylpyrrolidine-2-carboxamide 4 was found to be a highly efficient organocatalyst for the Michael addition, and the corresponding Michael adducts were obtained in good yields (up to 94%), with excellent enantioselectivities (up to 99% ee) and diastereoselectivities (up to 99:1 dr). 相似文献
11.
Gaëlle Fourrière 《Tetrahedron》2010,66(22):3963-3972
The synthesis of difluorinated carbocyclic analogues of 5-deoxypentofuranoses and 1-amino-5-deoxypentofuranoses is described. The sequence involves an addition of PhSeCF2TMS to carbohydrate-derived aldehydes or their corresponding tert-butanesulfinylimines followed by a radical cyclization. Optimized conditions for the PhSeCF2TMS addition to α-chiral aldehydes have been disclosed and its unusual diastereoselectivity is discussed. Application of the sequence using Ellman's auxiliary allows a more direct access to 1-aminopentose analogues with a complete control of the pseudo-anomeric center configuration. 相似文献
12.
《Tetrahedron: Asymmetry》2006,17(23):3300-3303
This paper reports the regio-, diastereo- and highly enantioselective vinylogous aldol reaction of 2-trimethylsilyloxyfuran (TMSOF) promoted by the SiCl4/Lewis base catalytic system. Several electron-pair donors proved to be effective as SiCl4 activators versus the TMSOF γ-selective addition to aldehydes giving rise to different diastereoisomeric ratios, while Denmark’s chiral bis-phosphoramide (R,R)-7 gave the highest enantioselectivity for both the anti- and syn-diastereoisomers. Furthermore, by using ambident electrophiles such as α,β-unsaturated aldehydes, the SiCl4/Lewis base-promoted process leads exclusively to the 1,2-addition products. 相似文献
13.
In this paper, one-pot synthesis of 2,4,6-triarylpyridine by condensation of subsisted acetophenone (II), aromatic aldehydes (I), and ammonium acetate (III) in the presence of nanocrystalline MgAl2O4 as a new heterogeneous catalyst under solvent-free conditions is reported. Advantages of this method are the use of spatially-hindered aldehydes such as 2-methoxy-, 2-fluoro-, and 2-chlorobenzaldehydes, a new nanocatalyst with high surface area, shorter reaction time, easier workup, higher yield, and its environmental friendliness. The performance of this reaction under solvent free conditions using heterogeneous catalysts like MgAl2O4 could enhance its efficiency from an economic as well as green chemistry point of view. 相似文献
14.
Enantioselective organocatalytic Michael addition of malonates to α,β-unsaturated aldehydes in water
Anqi Ma 《Tetrahedron letters》2008,49(19):3075-3077
The Michael addition of malonates to α,β-unsaturated aldehydes catalyzed by O-TMS protected diphenylprolinols and acetic acid in water occurs at 0 °C to rt. In most cases, the reaction runs to completion in less than 24 h. A wide range of aldehydes including β-aryl, β-alkyl and β-alkenyl acroleins are found to be compatible with these conditions, providing the corresponding adducts in good yields and with good to excellent enantioselectivities. 相似文献
15.
t-Butoxy derivatives of DIBALH [lithium diisobutyl-t-butoxyaluminum hydride (LDBBA), sodium diisobutyl-t-butoxyaluminum hydride (SDBBA), and potassium diisobutyl-t-butoxyaluminum hydride (PDBBA)] were examined as chemoselective reducing agents of carbonyl compounds. Among them, PDBBA was found to be the most efficient for the reduction of aldehydes and ketones to the corresponding alcohols in the presence of ester, amide, and nitrile substituents at ambient temperature. In addition, the optimal conditions gave higher chemoselectivity for aldehydes in the presence of ketones. 相似文献
16.
Cheng-Kun Lin 《Tetrahedron》2010,66(51):9688-9693
A simple method for the oxidation of primary alcohols to aldehydes using o-iodoxybenzoic acid (IBX) with the addition of stoichiometric acetic acid has been developed. Addition of acetic acid significantly accelerated the reaction rate. Under these conditions, primary aliphatic, benzylic, and allylic alcohols are smoothly converted to aldehydes in high yields (90-97%). 相似文献
17.
A general four-step approach to 1,2,3,7,8,8a-hexahydropyrido[4,3-d]pyrimidin-2-ones via Staudinger/intramolecular aza-Wittig reaction of 5-acyl-4-(β-azidoalkyl)-1,2,3,4-tetrahydropyrimidin-2-ones promoted by PPh3 was developed. Synthesis of the starting pyrimidinones included preparation of 3-azidoaldehydes by the addition of hydrazoic acid to α,β-unsaturated aldehydes, transformation of 3-azidoaldehydes into N-[(3-azido-1-tosyl)alkyl]ureas followed by the reaction with enolates of dibenzoylmethane, benzoylacetone, acetylacetone, or ethyl 2,4-dioxo-4-phenylbutanoate and dehydration of the resulting products under acidic conditions. 相似文献
18.
The BINOL ligand (R)-2 that contains bulky 3,3′-tertiaryalkyl groups shows improved catalytic properties over the previously reported 3,3′-substituted BINOL ligands in the asymmetric alkyne addition to aromatic aldehydes. It catalyzes the phenylacetylene addition to aromatic aldehydes with high enantioselectivity (86-94% ee) and good yields without using Ti(OiPr)4 and a Lewis base additive. The catalytic properties of several analogs of (R)-2 in the asymmetric alkyne addition to aldehydes have also been studied. 相似文献
19.
A series of chiral tetraaza ligands were studied for the enantioselective addition of dialkylzinc to aldehydes. These bis(amino amide) ligands show high enantioselectivity in the addition of organozincs to aromatic aldehydes. Different structural elements on the ligands seem to play an important role in determining the observed enantioselectivity. Ligand 4b (N,N′-bis(N-l-valinyl)-1,3-diaminopropane, with an aliphatic spacer with 3C atoms) catalyzed the addition of Et2Zn to benzaldehyde, 1-naphtaldehyde, 4-methoxybenzaldehyde, and 4-chlorobenzaldehyde to give the corresponding alcohol products with excellent conversions and selectivities and with enantioselectivities of 99, 97, 98, and 82%, respectively. DFT calculations provide an understanding of the mechanism of the enantioselection process. 相似文献
20.
Yuji Kurosaki 《Tetrahedron》2005,61(13):3289-3303
Lateral lithiation of (S)-4-isopropyl-2-(o-tolyl)oxazoline in diethyl ether followed by the reaction with aldehydes in the presence of TMEDA produced the addition products with stereoselectivities up to 84% de. Utilization of TMEDA as a ligand is essential for the good selectivity. Rationale for the stereoselectivity is proposed based on ab initio calculation of the lateral lithio species. The major (S,S)-products lactonized faster than the minor (S,R)-products to the corresponding 3,4-dihydroisocoumarins under acidic conditions. Thus, (3S)-3,4-dihydroisocoumarins were obtained in good optical purities up to 97% ee by sequential application of these matched stereoselective reactions. 相似文献