A New and Efficient Epoxide Ring Opening via Poor Nucleophiles: Indole, p-Nitroaniline, Borane and O-Trimethylsilylhydroxylamine in Lithium Perchlorate

Abstract

Highly regioselective ring opening of 2,3-dimethyloxirane, 2-epoxyphenylether and allyl(2-epoxymethyl) ether are observed through reactions with poor nucleophiles such as indole, borane, O-trimethylsilylhydroxylamine, p-nitroaniline and sterically hindered tert-butylamine in the presence of 5.0 M lithium perchlorate-Et 2 O solution. These reactions are fast, convenient, with rather high yields and are carried out at ambient temperatures.Key words: lithium perchlorate, epoxide, b-amino alcohols Oxiranes (epoxides) are widely distributed in nature and are of industrial and biochemical interest. In addition, they are becoming a powerful tool in the field of synthetic organic chemistry. 1 Epoxides are efficiently converted into functionalized alcohols by employing nucleophilic ringopening reactions. However, this reaction, which is usually carried out with a large excess of nucleophiles at elevated temperature with long reaction times and drastic conditions, often fails when poor nucleophiles and/or sterically bulky nucleophiles or epoxides are used. 2 Therefore, there is a significant current interest in the ring opening of epoxides.b-Amino alcohols constitute an important class of wellknown organic compounds that have importance in natural products, medicinal chemistry and other chemical fields. 3 The most practical and widely used method for preparing these compounds is the direct aminolysis of epoxides with an excess of amines or their synthetic equivalents at elevated temperatures. 4 Due to the elevated temperature, these reactions often fail when poorly nucleophilic or sterically bulky amines and in some case low boiling points amines are concerned. These are some significant limitations on the general utility of epoxide aminolysis. 5 To obviate these problems, several useful modifications activator/promoters have been reported: COCl 2 , 6 fluoro-alcohols as reaction media 7 (benzylic and aliphatic amines do not react under these conditions), Ti(O-i-Pr) 4 , 8 SmI 2 and SmCl 3 , 9 metal triflates, 10 metal amides, 11 Mg, Li, Pb, Sn, Si (an important drawback of these methods is that epoxides bearing a-hydrogens, frequently undergo rearrangement to produce allyl alcohols and primary amines show no regioselectivity). Good regioselectivity of ring opening by nucleophiles has been observed with LiClO 4 . 12 However, with this catalyst, deactivated aromatic amines and some sterically hindered amines fail to open up epoxides or require high temperature or pressure. Although a wide choice of promoters is available many are associated with one or other drawback. Hence, there is a need for new versatile methods.In the course of our investigations toward the development of new reactions promoted by lithium perchlorate in Et 2 O (LPDE) solution, we have found that 5.0 M LPDE solutions promote the addition of deactivated p-nitroaniline and secondary amines to epoxides under mild experimental conditions (r.t., 30 min). 13 The reaction was highly regioselective as 3 was the only detectable product. The results are summarize...

Synthesis and Characterization of Nickel(II) Aminoalkoxides: Application to Molecular Precursors for MOCVD of Ni Thin Films

“…The nickel atom forms an inversion center. The bond lengths of Ni1-O1 and Ni1-N1 are 1.837(3) and 1.937(3) Å, respectively, and are very similar to those of tetra-coordinated nickel complexes [54] and slightly longer than those of bis(β-ketoamino)nickel complexes. [55] They are shorter than the metal-atom distances reported in six-coordinate nickel(II) complexes.…”

“…Nickel hexamine dichloride was prepared as reported in literature. [60] Functionalized bidentate alcohols, such [54,61] and dried under nitrogen prior to use. 1 H and 13 C NMR spectra were recorded at 300 MHz on a Bruker DPX 300 MHz FT NMR spectrometer.…”

Synthesis, Antibacterial and Antitubercular Evaluation of Cardanol and Glycerol‑Based β-Amino Alcohol Derivatives

“…Usually, it is necessary a catalyst to perform epoxide aminolysis with poor nucleophiles. 61 The new compounds synthesized were completely characterized by their spectral data before proceeding for antimicrobial evaluation.…”

“…Usually, it is necessary a catalyst to perform epoxide aminolysis with poor nucleophiles. 61 The new compounds synthesized were completely characterized by their spectral data before proceeding for antimicrobial evaluation.The β-amino alcohols 2a-2o were examined for antibacterial and antitubercular activities using methods previously reported. 59 The results are shown in Table 2.…”

Enzymatic Synthesis of Enantiomerically Pure β‐Amino Ketones, β‐Amino Esters, and β‐Amino Alcohols with Baeyer–Villiger Monooxygenases

“…Furthermore, the reduction of amino acids to the corresponding amino alcohols is economically feasible only for the naturally occurring l-amino acids. The only synthetic methodologies available for the direct synthesis of amino alcohols in high yields are the enantioselective amination of chiral epoxides, [32][33][34] the directed reductive amination of b-hydroxy ketones, [35] the aminoacetoxylation of alkylenes, [36] and the asymmetric hydrogenation or reduction of prochiral b-amino ketones. [37] Although aminolysis of epoxides suffers from the limitations that chiral epoxides are not readily available, are expensive, and that only monosubstituted and trans-symmetrically substituted epoxides can be used, metal-based reactions on the other hand require expensive transition-metal elements (rhodium, [38] palladium, or ruthenium) and ligands such as BINAP.…”