- Cycloadditions between methyl (Z)-2-bromo-4,4,4-trifluoro-2-butenoate and various tosylacetamides: Synthesis of trifluoromethylated pyroglutamates and 2-pyridones derivatives
-
Cycloaddition reactions between methyl (Z)-2-bromo-4,4,4-trifluoro-2-butenoate and various 2-tosylacetamides are described. Various 2-tosylacetamides react with methyl (Z)-2-bromo-4,4,4-trifluoro-2-butenoate in the presence of NaH at room temperature in one step to form trifluoromethylated pyroglutamates as single diastereomers. However, employing the same reactants using t-BuOK as base at ?78 °C results in the formation of trifluoromethylated 2-pyridones. A ring-closure mechanism is proposed for the reaction.
- Zhang, Hong-Hai,Shen, Wei,Lu, Long
-
-
Read Online
- Highly diastereoselective synthesis of optically pure trifluoromethyl- substituted imidazolidine, oxazolidine and thiazolidine
-
Optically pure trifluoromethylated imidazolidine, oxazolidine, and thiazolidine derivatives were synthesized through double Michael addition of chiral amino amides, amino acids, or amino alcohols to an easily available trifluoromethyl building block methyl (Z)-2-bromo-4,4,4-trifluoro-2-butenoate. These reactions occurred highly diastereo-selectively (up to 99:1) in good yields (65-96%) under mild conditions.
- Zhang, Honghai,Shen, Qilong,Lu, Long
-
supporting information; experimental part
p. 349 - 351
(2011/02/28)
-
- Domino Cu-catalyzed C-N coupling/hydroamidation: A highly efficient synthesis of nitrogen heterocycles
-
(Chemical Equation Presented) Working in tandem: Highly functionalized pyrroles and pyrazoles can be synthesized from a domino Cu-catalyzed C-N coupling/hydroamidation sequence. The scope and the generality of the method is noteworthy as a wide variety of substituents, either in the alkene or alkyne counterparts, are well tolerated.
- Martin, Ruben,Rivero, Marta Rodriguez,Buchwald, Stephen L.
-
p. 7079 - 7082
(2007/10/03)
-
- ALKYL (E)- AND (Z)-2,3-DIBROMOPROPENOATES AS PRECURSORS TO 3-SUBSTITUTED ALKYL (E)- AND (Z)-2-BROMOPROPENOATES, 2,3-DISUBSTITUTED ALKYL (Z)- AND (E)-PROPENOATES AND SOME HETEROCYCLIC COMPOUNDS
-
3-(1-alkynyl)- and 3-aryl-substituted alkyl (Z)- and (E)-2-bromopropenoates have been stereospecifically and regioselectively synthesized by Pd-catalyzed cross-coupling reactions between 1-alkynylzinc chlorides, arylzinc chlorides or aryltributylstannanes and alkyl (Z)- and (E)-2,3-dibromopropenoates, (Z)- and (E)-2, respectively.The catalyst precursor consisting of a mixture of Pd on carbon and 3.9 equivalents of AsPh3 as well as that obtained by treatment of Pd(OAc)2 with 4 equivalents of AsPh3 in THF at 60 deg C can conveniently replace Pd(PPh3)4 in the reactions between (Z)- or (E)-2 and aryl or 1-alkynylzinc halides.On the other hand, a representative alkyl (Z)-3-alkyl-2-bromopropenoate has been prepared by reaction of a 9-alkyl-9-BBN derivative with (Z)-2a in DMF solution, in the presence of K2CO3 and a catalytic quantity of PdCl2(dppf).Some applications demonstrate the synthetic utility of 3-aryl-substituted alkyl (Z)- and (E)-propenoates, (Z)- and (E)-4.Thus, ethyl (E)-2-bromo-3-propenoate, (E)-4e, represents a direct precursor to 3-bromocoumarin, 7, and compound (Z)-8, which is obtained by acidic hydrolysis of (Z)-4e, undergoes a Pd-catalyzed intramolecular carbonylation reaction, which affords 3-ethoxycarbonylcoumarin, 9, in high yield.Moreover, treatment of compounds (Z)- and (E)-4 with organozinc or organotin derivatives, in the presence of catalytic amounts of a suitable Pd catalyst, affords, stereospecifically and in satisfactory to excellent yields, trisubstituted α,β-unsaturated esters, (E)- and (Z)-10, respectively, which cannot be easily prepared in stereoisomerically pure form by classical procedures.One of these esters, i.e. compound (E)-10c, represents a direct precursor to an isoaurone, i.e. (E)-3- benzylidenebenzofuran-2-one, (E)-11.Finally, a representative stereodefined unsymmetrically 2,3-diaryl-disubstituted alkyl propenoate has been synthesized by a one-pot procedure involving two sequential palladium-catalyzed arylations of (Z)-2a.
- Rossi, Renzo,Bellina, Fabio,Carpita, Adriano,Gori, Raffaele
-
p. 381 - 392
(2007/10/02)
-
- Highly Regioselective Palladium-Mediated Synthesis of Stereoisomerically Pure (Z)- and (E)-Alkyl 2-Bromo-3-(hetero)arylpropenoates
-
Stereoisomerically pure (Z)- and (E)-alkyl 2-bromo-3-(hetero)arylpropenoates, (Z)- and (E)-2, have been efficiently and selectively prepared by Pd(0)-mediated cross-coupling reaction between (hetero)arylzinc halides, 5, and easily available (Z)- and (E)-a
- Bellina, Fabio,Carpita, Adriano,Santis, Massimo De,Rossi, Renzo
-
p. 6913 - 6916
(2007/10/02)
-
- HALOGENATION OF UNSATURATED ESTERS-II. ADDITION OF Cl2, BrCl AND Br2 TO METHYL ESTERS OF MONOCHLOROPROPENOIC ACIDS
-
The addition of chlorine, bromine chloride and bromine to methyl 2-chloropropenoate 1, methyl cis-3-chloropropenoate 2 and methyl trans-3-chloropropenoate 3 under ionic and radical conditions gave regioisomer mixtures.Both trans- and cis-addition of halogen species was observed, bromine preferentially adding to the non-halogenated carbon atom.
- Pitkaenen, Maija,Korhonen, Ilpo O. O.
-
p. 3367 - 3372
(2007/10/02)
-