127581-43-5

BuLi-Me2N(CH2)2OLi (BuLi-LiDMAE) promoted the clean C-6 functionalisation of 3-picoline via a methyl to C-6 lithium shift.

An organocatalyzed aerobic benzylic C-H oxidation of alkyl and aryl heterocycles has been developed. This transition metal-free method is able to overcome the electron-withdrawing effect as well as product-inhibition effects in heterobenzylic radical oxidation. A variety of ketones bearing N-heterocyclic groups could be prepared under relatively mild conditions with moderate to high yields.

A rhodium-catalyzed Suzuki-Miyaura coupling reaction via C(O)-C bond activation to form 2-benzoylpyridine N-oxide derivatives is reported. Both the C(O)-C(sp2) and C(O)-C(sp3) bond could be activated during the reaction with yields up to 92%. The N-oxide moiety could be employed as a traceless directing group, leading to free pyridine ketones.

Herein, we report an original one-step, simple, room-temperature, regioselective Minisci reaction for the acylation of electron-deficient heteroarenes with alkynes. The method has broad functional group compatibility and gives exclusively monoacylated products in good to excellent yields. The mechanistic pathway was analyzed based on a series of experiments confirming the involvement of a radical pathway. The 18O-labeling experiment suggested that water is a source of oxygen in the acylated product, and head space GC-MS experiment shows the C-C cleavage occurs via release as CO2.

A highly enantioselective transfer hydrogenation of non-ortho-substituted aryl N-heteroaryl ketones, using readily available chiral diamine-derived iridium complex (S,S)-1f as a catalyst and sodium formate as a hydrogen source in a mixture of H2O/i-PrOH (v/v = 1:1) under ambient conditions, is described. The chiral aryl N-heteroaryl methanols were obtained with up to 98.2% ee by introducing an N-oxide as a removable ortho-substituent. In contrast, no more than 15.1% ee was observed in the absence of an N-oxide moiety. Furthermore, the practical utility of this protocol was also demonstrated by gram-scale asymmetric synthesis of bepotastine besilate in 51% total yield and 99.9% ee.

The methylene group of various substituted 2- and 4-benzylpyridines, benzyldiazines and benzyl(iso)quinolines was successfully oxidized to the corresponding benzylic ketones using a copper or iron catalyst and molecular oxygen as the stoichiometric oxidant. Application of the protocol in API synthesis is exemplified by the alternative synthesis of a precursor to the antimalarial drug Mefloquine. The oxidation method can also be used to prepare metabolites of APIs which is illustrated for the natural product papaverine. ICP-MS analysis of the purified reaction products revealed that the base metal impurity was well below the regulatory limit.

A transition-metal-free, t-BuOOH mediated intramolecular carbonylation of arenes in 2-aryl-3-picolines via oxidative C-H functionalizations of the methyl group has been developed, providing an expedient synthesis of 4-azafluorenones. Distinct from the current literature wherein methylarenes have been used as acylating agents, 2-aryl-3-picolines in this study are transformed into aldehydes, which give 4-azafluorenones upon rapid intramolecular acylation. The study demonstrates the first example of intramolecular carbonylation of arenes utilizing a methyl group as latent carbonyl functionality.

Reaction of α-bromoisobutyrophenone on pyridine 1-oxide and γ and β-picoline 1-oxide, in the presence of silver nitrate, leads to N-alkoxypyridinium and picolinium salts, bearing a keto group on their alkoxyl chain.On treatment with pyrrolidine, these salts are converted to 4-ω-pyrrolidinobutadienyl-3-isoxazolinols, substituted or not by a methyl group in their chain.The reaction proceeds according to the PARC-ANRO mechanism (Proton Abstraction, Ring Closure-Addition of a Nucleophile, Ring Opening), as demonstrated by isolation of the bicyclic isoxazolino pyridinium intermediates which result from the first phase of this process.In addition, steric hindrance towards ring opening caused by the methyl group in the adduct derived from β-picolin N-oxide, allow observation of a competiting novel mode of fragmentation alkoxylogous of Katritzky's mode A of decomposition of N-alkoxypyridinium salts.

Isolation of intermediate isoxazolopyridinium salts ascertains earlier mechanistic assumption in a heterocyclic ring conversion of potential value for a new approach to terpenoid synthesis.