Reactions of nitrogen compounds with ruthenium tetroxide. 2. Oxidation of tertiary amines as a convenient alternative to von Braun degradation

Abstract

Notes 2-Chloromethyl-5-hydroxy-4-pyrone (3), mp 165-166 °C (lit.30 mp 166-167 °C).2-Hydroxymethyl-5-methoxy-4-pyrone (5), mp 119-120 °C (lit.31 mp 119-121 °C).2-Acetoxymethyl-5-aCetoxy-4-pyrone (6). This material was prepared by acetylation of kojic acid, mp 100-102 °C (lit.32 mp 102 °C).Comenic Acid (7). This.compound was prepared by catalytic oxidation pf kojic acid, mp 220 °C dec (lit.33 mp not specified).Hydroxymaltol (2-hydroxymethyl-3-hydroxy-4-pyrone) (9), mp 149-151 °C (lit.34 mp 152-153 °C).

RuO4-mediated oxidation of N-benzylated tertiary amines. 3. Behavior of 1,4-dibenzylpiperazine and its oxygenated derivatives

“…Oxidation was performed in the same conditions as above [2,3,7,8], that is with catalytic amounts of RuO 4 (generated in situ from catalytic RuO 2 and excess NaIO 4 ), in CCl 4 /water heterogeneous mixtures and at room temperature. The reaction mixtures were worked-up in two ways (A or B ; see Section 3.8), differing by the order of operations.…”

“…For instance, earlier studies indicated 4-benzoylmorpholine and 4-benzyl-3-morpholinone as reaction products obtained from 4-benzylmorpholine [2], meaning that both types of N -α-sites (i.e., exocyclic and endocyclic, respectively) were attacked. In the same reaction conditions, 1-benzylpiperidine yielded only products of endocyclic attack [3]. Same exclusive endocyclic functionalization showed also some piperazine derivatives (Scheme 1).…”

“…In the same paper [6], the authors claimed also that only 10 has resulted from 2,6-piperazinedione 9. Besides the endocyclic functionalization in all these cases, a simultaneous oxidative attack at both N 1 -CH 2 -CH 2 -N 2 methylene groups of 1 and 4 seems to have been in action, unlike the behavior of 1-benzylpiperidine [3].…”

“…It is known that the powerful oxidant ruthenium tetraoxide (RuO 4 ) functionalizes tertiary aliphatic amines at their N -α-positions to afford amides and/or dioxygenated compounds [1][2][3][4][5][6]. For instance, earlier studies indicated 4-benzoylmorpholine and 4-benzyl-3-morpholinone as reaction products obtained from 4-benzylmorpholine [2], meaning that both types of N -α-sites (i.e., exocyclic and endocyclic, respectively) were attacked.…”

RuO4-mediated oxidation of N-benzylated tertiary amines. 2. Regioselectivity for N,N-dimethyl- and N,N-diethylbenzylamine as substrates

“…In a previous paper 1 we studied the RuO 4 -mediated oxidation 2 of some N-benzylated cycloalkylamines and found that the attack occurs at both types of N-α-methylene positions, 3 i.e., endocyclic and exocyclic (benzylic). Proof of the incursion of the corresponding iminium cations as intermediates came from their capture as nitriles in the presence of cyanide anion (cyano trapping).…”