A New and Efficient One-pot Synthesis of Trialkyl 6-tert-Butylamino-2H-pyran-2-one-3,4,5-tricarboxylates

Abstract

The highly reactive 1:1 intermediate produced in the reaction between tert-butyl isocyanide and dialkyl acetylenedicarboxylates is trapped by dialkyl 2-bromomalonates to yield the title compounds in fairly high yields.2H-Pyran-2-one and its derivatives are important starting materials in the synthesis of cyclobutadienes. 1Y2 These heterocycles ¢nd use in cycloaddition reactions, providing bicyclolactone adducts which can be elaborated into a variety of highly functionalized cyclohexadienes and benzenes. 3À5 Current synthetic methodology for preparation of this class of compounds still remains fairly speci¢c. 6Y7 Here, a direct, e¤cient and operationally convenient approach to the synthesis of highly functionalized 2H-pyran-2-one derivatives 3 using dialkyl 2-bromomalonates 2 is presented. Thus, reaction of tert-butyl isocyanide with dialkyl acetylenedicarboxylates 1 in the presence of a strong CH-acid such as 2 leads to the corresponding 2H-pyran-2-one derivatives 3 (Scheme 1).The three-component condensation reactions produce the hitherto unknown functionalized 2H-pyran-2-ones 3 in high yields. The structures of the isolated crystalline compounds 3a ^d were deduced from elemental analyses, 1 H and 13 C NMR spectroscopy. IR spectroscopy was applied to distinguish 3 from the primary product, ketenimine 5 (Scheme 2), which apparently undergoes further transformations to produce the 2H-pyran-2-one ring system under the given reaction conditions. Thus, the IR spectra of the isolated products showed strong NH stretching bands at ca. 3225^3210 cm À1 for alkylamino groups. Further evidence was obtained from proton couple 13 C NMR spectra which showed no methine carbon resonance.

UV spectrophotometric study of the kinetics and mechanism of the reactions between triphenylphosphine, dialkyl acetylenedicarboxylates and NH-acid

“…Proposed mechanism for the reaction between 1, 2 (2a, 2b or 2c) and 3 based on previous reports [13][14][15][16][17][18][19][20][21][22][23][24][25][26] for the generation of phosohorus ylides 4 (4a, 4b or 4c). spectrophotometer cell, was employed throughout the current work.…”

“…These are most often obtained in excellent yields from the 1:1:1 addition reaction between triphenylphosphine and dialkyl acetylenedicarboxylates, in the presence of strong CH-, SH-or NHacids [13][14][15][16][17][18][19][20][21][22][23][24][25]. A facile synthesis of the reaction between triphenylphosphine 1, dialkyl acetylendicarboxylates 2 (2a, 2b or 2c) and 2,3-di-hydroxybenzaldehyde 3 (an NH-acid) has been reported [26], however, the kinetic studies of these reactions have not been investigated yet.…”

Synthesis of stable phosphorus ylides from 3, 5-dimethylpyrazole and kinetic investigation of the reactions by UV spectrophotometry

“…The synthetic reactions between triphenylphosphine 1, dialkyl acetylenedicarboxylates 2 and CH, SH or NH-acids have been reported earlier [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32] but the kinetic study of these reactions has not been investigated yet. Herein, we wish to describe a kinetic investigation of the current synthesis.…”

Chemoselective synthesis of dialkyl 2-(tert-butylamino)- 6-methyl-5-trifluoroacetyl-4H-pyran-3,4-dicarboxylates

“…The reaction of tert butyl isocyanide with a triple carbon-carbon bond tends to occur in a stepwise manner via a zwitterionic intermediate, fate of which appears to be dictated by the nature of the original acetylenic com pound. [2][3][4][5][6] In this work, we present a direct, efficient, and operationally convenient approach to the chemoselective synthesis of polyfunctionalized 4Н pyrans using a strong CH acid. 1,1,1 Trifluoropentane 2,4 dione (1) is a β diketone with a strong electron withdrawing CF 3 group; therefore, it can be such a strong CH acid (or OH acid in the form of an enol tautomer).…”