ChemInform Abstract: NEW α‐OXO‐Γ‐(ENAMINOALKYL)TRIPHENYLPHOSPHONIUM SALTS AND YLIDES FROM ISOXAZOLE DERIVATIVES‐ SYNTHESIS OF α,Γ‐DIOXOX OLEFINS

Abstract

Zur Synthese von oqy‐Dioxo‐Olefinen werden z.B. die Chlorderivate der Oxime (I) mit Propargylbromid kondensiert und die entstehenden 5‐Brommethyl‐isoxazole in situ in die Phosphoniumbromide, (II) I′ übergeführt oder ähnlich die Chlor‐oxime (III) mit 4‐Oxo‐pentin‐(2) zu den Ketonen (IV) cyclisiert und diese nach der Reduktion der Ketogruppe in die Phosphoniumbromide (V) übergeführt.

Synthesis, Biological Evaluation, and Structure−Activity Relationships for 5-[(E)-2-Arylethenyl]-3-isoxazolecarboxylic Acid Alkyl Ester Derivatives as Valuable Antitubercular Chemotypes

“…1 H NMR and 13 C NMR spectra were recorded on a Bruker spectrometer at 400 and 100 MHz, respectively, with TMS as an internal standard. 19 F NMR spectra were recorded on Bruker spectrometer at 376 MHz with TFA as an external standard. Standard abbreviation indicating multiplicity was used as follows: s = singlet, d = doublet, dd = doublet of doublets, t = triplet, q = quadruplet, m = multiplet, and br = broad.…”

“…4 General Procedure for the Synthesis of 6-26, 28-37, and 47. To a stirred mixture of (3-ethoxycarbonyl-5-isoxazolylmethyl)triphenylphosphonium bromide 19 (5) (1 equiv) or (5-bromomethylisoxazole)triphenylphosphonium bromide 20 (51) (1 equiv) in anhydrous THF at -78 °C, sodiumbistrimethylsilylamide (1.05 equiv) was added dropwise. After 0.5 h, the appropriate aldehyde (1 equiv) in anhydrous THF was added dropwise and the reaction mixture was stirred at rt until consumption of the starting material according to TLC.…”

“…The target compounds 6 − 26 , 28 − 37 , and 47 were synthesized by employing straightforward and efficient Wittig protocols (Scheme ). (3-Ethoxycarbonyl-5-isoxazolylmethyl)triphenylphosphonium bromide ( 5 ) and (5-isoxazolylmethyl)triphenylphosphonium bromide ( 51 ) were prepared as described previously. A dipolar cycloaddition reaction of the nitrile oxide derived from ethyl 2-chloro-2-(hydroxyimino)acetate with propargyl bromide gave the 5-bromomethylisoxazole derivative 4 , which was subsequently reacted with triphenylphosphine in THF to give the salt 5 .…”

“…1 H NMR (CDCl 3 ) δ 1.45 (t, J = 7.2 Hz, 3H), 4.47 (q, J = 7.2 Hz, 2H), 6.71 (s, 1H), 6.85-6.98 (m, 2H), 7.04 (d, J = 16.8 Hz, 1H), 7.45 (d, J = 16.8 Hz, 1H), 7.50-7.62 (m, 1H). 19 F NMR (CDCl 3 ) δ -111.9 (d, J = 8.0 Hz), -108.1 (d, J = 8.0 Hz). HRMS (ESI) calculated for C 14 H 11 F 2 NO 3 [M þ H] þ 280.0779, found 280.0793.…”

“…1 H NMR (CDCl 3 ) δ 1.45 (t, J = 7.2 Hz, 3H), 2.28 (s, 3H), 4.47 (q, J = 7.2 Hz, 2H), 6.74 (s, 1H), 7.05-7.18 (m, 2H), 7.31 (d, J = 16.8 Hz, 1H), 7.58 (d, J = 16.8 Hz, 1H). 19 (18). 27 Purified by column chromatography (EtOAchexane 1:4) followed by recrystallization with EtOH.…”