α-Organoelement Nitrones:  Synthesis, Properties, and IR and ¹³C NMR Spectral and X-ray Structural Characterization

Abstract

α-Organoelement-substituted nitrones have been synthesized for the first time through the reaction of the α-lithiated cyclic aldonitrones of 3-imidazoline 3-oxide, pyrroline 1-oxide, 2H-imidazole 1-oxide, and 3,4-dihydroisoquinoline 2-oxide series with electrophilic reagents such as HgCl2, (CH3)3SiCl, (C2H5)3GeCl, (n-C4H9)3SnBr, Ph2P(O)Cl, Ph2PCl, PhSSPh, PhSeSePh, TsCl, and TsF. Aldonitrones of the 3-imidazoline 3-oxide and pyrroline 1-oxide series were shown to readily afford the products of the lithiation−electrophilic substitution reaction. In contrast, aldonitrones of the 2H-imidazole 1-oxide and 3,4-dihydroisoquinoline 2-oxide series react smoothly only with halogen-free electrophiles. It was found that an aldonitrone group could be lithiated and selectively reacted with electrophiles even when kinetically more acidic methylene and amino groups are present in the molecule. Characteristic features of IR and 13C NMR spectra of the compounds synthesized are discussed. Selected α-organoelement nitrones are characterized by an X-ray diffraction study.

Reaction of Paramagnetic Synthon, Lithiated 4,4,5,5‐Tetramethyl‐4,5‐dihydro‐1H‐imidazol‐1‐oxyl 3‐oxide, with Cyclic Aldonitrones of the Imidazole Series

“…The only close analogy of such a process may be the formation of a vicinal diradical by the reaction of two equivalents of compound 1 with quinoxaline 1,4‐dioxide . Another interesting characteristic of aldonitrones 2 and 4 is their “dual” nature (Umpolung character), which means that in the presence of strong bases, they can generate dipole‐stabilized organolithium intermediates that are capable of reacting further with either the excess of the un‐ionized substrate (to form dimeric structures) or an extraneous electrophilic reagent that was added to the reaction . These circumstances make the reaction of lithium derivative 1 with aldonitrones of the imidazole series a rather serious challenge for a researcher.…”

Peculiarities of chemical properties of cyclic nitrones and their use in organic synthesis

“…The reaction with TsCl gives α-chloro nitrone 22f, and with TsF, the corresponding sulfonyl derivative 22g. Using HgCl 2, Et 3 GeCl, n-Bu 3 SnBr as electrophilic reagents, the synthesis of nitrones containing an α-carbon-metal bond 22h-j and 23k has been carried out for the first time 21,22 (Scheme 9). h: E = HgCl 2 ; R = HgCl i: E = (C 2 H 5 ) 3 GeCl; R = Ge(C 2 H 5 ) 3 j: E = (n-C 4 H 9 ) 3 SnBr; R = Sn(n-C 4 H 9 ) 3 k: E = HgCl 2 ; 0.5 equiv…”

Mercury(II) Chloride

“…4 If only 0.5 equivalents of HgCl 2 are used in the reaction, a disubstituted mercuric derivative is formed. 5 (G) Reduction of a Benzo [b]furan Ester Varadaraju and Hwu reported the stereoselective reduction of a benzo[b]furan ester with metallic magnesium, catalytic HgCl 2 , and methanol as the solvent. 18 The product is a (±)-trans-dihydrobenzo[b]furan.…”

“…Mercury(II) chloride, HgCl 2 , is a commercially available mercury salt, and thus an important mercury(II) source. Besides novel mercuration reactions with organic substrates, [3][4][5][6][7] HgCl 2 has been extensively used in a variety of cyclization reactions, forming both carbocycles and heterocycles. [8][9][10] Its use as inorganic thiophile has led to the formation of several new products from organosulfur reactants, especially thiocarbonyl compounds.…”