N,N'-Bis(2,2,2-trifluoroethyl)-N,N'-ethylenetartramide: An Improved Chiral Auxiliary for the Asymmetric Allylboration Reaction
摘要:
N,N-Bis(2,2,2-trifluoroethyl)-N,N'-ethylenetartramide (8), synthesized by a simple four-step sequence from ethylenediamine and benzylidenetartaric acid, was designed in anticipation that the derived allylboronates 9-11 would display enhanced reactivity owing to the inductive effect of the N-trifluoroethyl substituents that would increase the Lewis acidity of the boron atom of the B-allyl-1,3,2-dioxaborolanes. Reagents 9-11 were synthesized by transesterification of 8 with the crystalline and easily purified allylboronate diethanolamine complexes 13, 19, and 25. Allylboronate 9 is ca. 100-fold more reactive than 6 and is also substantially more useful than the previously reported allyboronate 4, which suffers from very poor solubility in toluene at -78 degrees C. Most importantly, allylboronates 9-11 are significantly more enantioselective than the parent tartrate allylboronates 1-3 and rank among the most highly enantioselective allylboron reagents yet reported. Reactions of 9-11 with aldehydes are performed in THF at- -78 or -55 degrees C for 5-12 h periods. The enantioselectivity realized in reactions with achiral aldehydes is 92-95% ee (Table 2), and excellent diastereoselectivity is achieved in double asymmetric reactions with chiral aldehydes 15a, 15b, and 33 (Tables 3 and 4). For example, 16 and 28 are now available with a minimum selectivity of 92% from reactions of 15a and 15b with allylboronate 9, while the crotylboration products 29, 30, and 31 are available with a minimum selectivity of 90% (usually greater than or equal to 95%) from reactions of 15a and 15b with crotylboronates 10 and 11; the fourth isomer, 32a, is available with 83% selectivity. Chiral reagents 9-11 thus appear well suited for application to complex problems in organic synthesis.
Interaction of fluorine-containing 1,3-dicarbonyl compounds with polyamines
摘要:
In the reaction of fluorinated copper(II) 1,3-diketonates with diethylenetriamine (or triethylenetetramine) in CHCl3, N,N'-bis(1,3-aminovinylketones) are formed in 21-35% yields. Fluorine-containing 1,3-diketones and 1,3-ketoesters, upon interaction with polyamines without solvent, undergo acid cleavage, forming the corresponding amides. The copper(II) 1,3-ketoesterates are readily cleaved in CHCl3 at 25-degrees-C in excess triethylenetetramine or ethylenediamine.
Convenient One-Pot Synthesis
of N-Substituted 3-Trifluoroacetyl Pyrroles
作者:Nilo Zanatta、Ana Wouters、Leonardo Fantinel、Fabio da Silva、Rosemário Barichello、Pedro da Silva、Daniela Ramos、Helio Bonacorso、Marcos Martins
DOI:10.1055/s-0028-1087821
日期:——
A new one-pot strategy for the synthesis of a series of new N-substituted 3-trifluoroacetyl pyrroles is presented. These compounds were obtained by the reaction of 3-trifluoroacetyl-4,5-dihydrofuran with primary amines, which generated 1,1,1-trifluoro-3-(2-hydroxyethyl)-4-alkylaminobut-3-en-2-one intermediates. In most cases these intermediates were not stable enough to be isolated. Thus, in the same
THE REACTION OF ACETIC AND TRIFLUOROACETIC ANHYDRIDES WITH SOME SUBSTITUTED GUANIDINE HYDROCHLORIDES
作者:W. F. Cockburn、R. A. B. Bannard
DOI:10.1139/v57-171
日期:1957.11.1
Acetylation of the hydrochlorides of guanidine, cyclohexylguanidine, and 1-guanylpiperidine has been found to yield substituted triazines. Trifluoroacetylation of 1-guanylpiperidine hydrochloride also gives a triazine, whereas guanidine hydrochloride and cyclohexylguanidine hydrochloride are converted to bistrifluoroacetyl derivatives. The same triazines can also be obtained by acylation of the appropriate
Ethyl trifluoroacetate: a powerful reagent for differentiating amino groups
作者:Daqiang Xu、Kapa Prasad、Oljan Repic、Thomas J. Blacklock
DOI:10.1016/0040-4039(95)01655-4
日期:1995.10
Selective protection of primary amines in the presence of secondary amines and monofunctionalization of symmetric primary and secondary diamines using ethyl trifluoroacetate is described. Effective differentiation of primary, secondary and tertiary alkyl-substituted primary amines from one another by ethyl trifluoroacetate acylation is also demonstrated. These results are explained on the basis of
A facile access to new diazepines derivatives: Spectral characterization and crystal structures of 7-(thiophene-2-yl)-5-(trifluoromethyl)-2,3-dihydro-1 H -1,4-diazepine and 2-thiophene-4-trifluoromethyl-1,5-benzodiazepine
作者:Guillermo Ahumada、David Carrillo、Carolina Manzur、Mauricio Fuentealba、Thierry Roisnel、Jean-René Hamon
DOI:10.1016/j.molstruc.2016.07.047
日期:2016.12
and ethylenediamine. Compounds 1–3 were fully characterized by elemental analysis, FT-IR and multinuclear ( 1 H, 13 C and 19 F) NMR spectroscopy. In addition, their molecular identities and geometries have been authenticated by single-crystal X-ray diffraction analysis. The spectroscopic and structural data confirm that the 1,4-diazepine 2 and the 1,5-benzodiazepine 3 exist in the imine-enamine and