1,611 research outputs found
Double Michael adducts: Source for spiro heterocycles
No full text283-289The gem cyano ester functionality in double
Michael adduct, 4-carboethoxy-2-carbomethoxy-4-cyano-3,5-diaryltetra-hydro[2H]thiopyran-1,1-dioxide 1 has been exploited to develop three
different types of spiro heterocycles viz.,
spiro pyrimidine, pyrazole and isoxazole derivatives in the presence of
appropriate nucleophiles
Stereoselective Synthesis of Spiro-Decalin Oxindole Derivatives via Sequential Organocatalytic Michael–Domino Michael/Aldol Reaction
No full textA highly stereoselective procedure for the synthesis
of spiro-polycyclic
oxindoles bearing five contiguous stereogenic centers including two
tetrasubstituted carbons has been developed. Under sequential organocatalysis
performed by a pyrrolidine-based organocatalyst and DBU, a highly
atom-economical Michael–domino Michael/aldol reaction sequence
was optimized, yielding variously functionalized spiro-decalin oxindoles
with excellent stereoselectivity (>99:1 dr, up to 92% ee)
Organocatalytic synthesis of spiro compounds via a cascade Michael–Michael-aldol reaction
No full textThe synthesis of spiro compounds via a Michael-Michael-aldol reaction is reported. The reaction affords spirooxindole derivatives in good yields and in almost diastereo- and enantiopure form. Moreover, the reaction works with several heterocycles such as oxindoles, benzofuranones, pyrazolones or azlactones rendering the final spiro compounds in good yields and excellent stereoselectivities
Stereoselective Synthesis of Spiro-Decalin Oxindole Derivatives via Sequential Organocatalytic Michael–Domino Michael/Aldol Reaction
No full text[Image: see text] A highly stereoselective procedure for the synthesis of spiro-polycyclic oxindoles bearing five contiguous stereogenic centers including two tetrasubstituted carbons has been developed. Under sequential organocatalysis performed by a pyrrolidine-based organocatalyst and DBU, a highly atom-economical Michael–domino Michael/aldol reaction sequence was optimized, yielding variously functionalized spiro-decalin oxindoles with excellent stereoselectivity (>99:1 dr, up to 92% ee)
Multicomponent Synthesis of Spiro-dihydropyridine Oxindoles <i>via</i> Cascade Spiro-cyclization of Knoevenagel/Aza-Michael Adducts
No full textAn
efficient, straightforward, and one-pot synthesis
of biologically
relevant spiro-dihydropyridine oxindoles was described via readily available isatin, malononitrile, allenoate, and amines.
The metal/organocatalyst-free, Et3N-mediated reaction proceeds via cascade spiro-cyclization of in situ generated Knoevenagel/aza-Michael adducts. The reaction has great
flexibility over electron-rich and electron-poor substituents affording
desired products in good to excellent yields. We have also demonstrated
the selected spiro-dihydropyridines for late-stage diversification
into new spiro-dihydropyridine hybrids of pharmaceutical relevance
Highly Enantioselective Construction of Spiro[4H-pyran-3,3 '-oxindoles] Through a Domino Knoevenagel/Michael/Cyclization Sequence Catalyzed by Cupreine
No full textThe first enantioselective organocatalytic two- and three-component reactions via a domino Knoevenagel/Michael/cyclization sequence with cupreine as catalyst have been developed. A wide range of optically active spiro[4H-pyran-3,3'-oxindoles] were obtained in excellent yields (up to 99%) with good to excellent enantioselectivities (up to 97%) from simple and readily available starting materials under mild reaction conditions. These heterocyclic spirooxindoles will provide promising candidates for chemical biology and drug discovery
Organocatalytic Aza-Michael/Michael Cyclization Cascade Reaction: Enantioselective Synthesis of Spiro-oxindole Piperidin-2-one Derivatives
No full textA simple,
direct, and highly enantioselective synthesis of spiro-oxindole
piperidin-2-one derivatives was achieved through an aza-Michael/Michael
cyclization cascade sequence using a squaramide catalyst. The desired
products were obtained in excellent yields (up to 99%) and good to
high stereoselectivities (up to >20:1 dr and up to 99% ee) under
mild
conditions
Michael adducts: Source for spiro heterocycles
No full text1473-1478<span style="font-size:12.0pt;font-family:
" times="" new="" roman";mso-fareast-font-family:"times="" roman";mso-ansi-language:="" en-gb;mso-fareast-language:en-us;mso-bidi-language:ar-sa"="" lang="EN-GB">The double Michael
adducts have been conveniently exploited to develop a new class of spiro
heterocycles having thiandioxide moiety in combination with pyrazole, isoxazole
and pyrimidine derivatives adopting simple and versatile synthetic
methodologies.</span
Organocatalytic oxa/aza-Michael–Michael Cascade Strategy for the Construction of Spiro [Chroman/Tetrahydroquinoline-3,3′-oxindole] Scaffolds
No full textA new useful and effective chiral amine-catalyzed oxa- and aza-Michael–Michael cascade methodology for the construction of enantiomerically enriched indolinones spiro-fused with chromans or tetrahydroquinolines is reported. By employing suitable organocatalysts depending on the different Michael donors (Ar-OH/Ar-NHR), the processes offered excellent stereocontrol (dr >20:1, >99% ee) under mild conditions
Highly diastereoselective synthesis of spiro[tetrahydrothiophene-3,3′-pyrazol] with an all-carbon quaternary stereocenter via [3 + 2] cascade Michael/Michael cyclization catalyzed by DABCO
No full textThe diastereoselective formation of spiro[tetrahydro thiophene-3,3′-pyrazol] derivatives has been achieved via a Michael/Michael cyclization reaction. The reaction was performed using trans-ethyl 4-mercapto-2-butenoate 1 with various 4-benzylidene-5-methyl-2-phenylpyrazolones 2 catalyzed by 1,4-diazabicyclo[2.2.2]octane (DABCO) in toluene at 0 °C. The reaction proceeds rapidly and affords the corresponding spiro[tetrahydrothiophene-3,3′-pyrazol] derivatives in excellent yields and moderate to excellent diastereoselectivities (up to 98% yield and >20:1 dr).</p
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