Ketene. Part 26. The reactions of 3,4-dihydroisoquinoline N-oxide with ketenes, and an attempted synthesis of 3,4-dihydro-3,3-dimethylquinoline N-oxide

Abstract

The reactivity of 3,4‐dihydroisoquinoline N‐oxide (I) (with restricted relative orientation of the aromatic moiety and the nitrone function), which is known to be highly reactive in 1,3‐dipolar cycloadditions, is studied employing various ketenes.

An Improved Procedure for the Preparation of 2,2-Bis[2-[4(S)- tert-butyl-1,3-oxazolinyl]]propane [(S,S)-tert-Butylbis(oxazoline)] and Derived Copper(II) Complexes

“…Dimethylmalonic acid (5) was prepared according to literature procedures. 14 All other chemicals were obtained from commercial sources and used without further purification, except for p-toluenesulfonyl chloride, which was recrystallized prior to use. Flash chromatography was performed using EM Reagent silica gel 60 (230-400 mesh).…”

“…( S )- tert -Leucine ( 2 ) was a gift from NSC Technologies. Dimethylmalonic acid ( 5 ) was prepared according to literature procedures . All other chemicals were obtained from commercial sources and used without further purification, except for p -toluenesulfonyl chloride, which was recrystallized prior to use.…”

“…While the ( S )- tert -leucinol may purified by vacuum distillation (79%), the yields of the overall process are improved by employing the unpurified alcohol 3 in the subsequent acylation step with dimethylmalonyl dichloride 6 to form the dihydroxy malonodiamide 7 , mp 163.3−163.7 °C, in 88% overall yield from ( S )- tert -leucine ( 2 ) after recrystallization. Although dimethylmalonic acid ( 5 ) is commercially available, nitric acid oxidation of 2,2-dimethyl-1,3-propanediol ( 4 ) significantly increases the cost-effectiveness of the overall synthesis.

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Transformation of Zwitterionic Pyridine Derivatives to a Spiro-Fused Ring System: Azoniabenzo[de]fluorine. Synthesis and Mechanistic Rationalization

“…The computed solvent-phase free energy profile for the transformation of 1a, obtained for dichloromethane solution using and diphenylketene. On the basis of experimental data 19,20 or computational mechanistic analyses, 21 ketenes have been suggested to react with various 1,3-dipoles in a stepwise fashion, but the situation is less clear for the closely related keteneimines where concerted 22 and stepwise 23 reactions with 1,3-dipoles have both been proposed. For the present cyclization, we found that the reaction takes place in two steps.…”

One-Step Synthesis for the Preparation of Quinoline Alkaloid Analogues

“…At first, our team focused on preparing the simplest member of the target molecules, 3,3-dimethylquinoline-2,4-dione ( 1 , R = R‘ = Me). A rather complex method for preparing this compound was proposed by Evans et al in 1987 using strong reaction conditions to cyclize the corresponding anilide by phosphorus pentoxide . Our first attempt was based on the reaction between 2-methyl-4 H- 3,1-benzoxazin-4-one and an appropriate precursor of 4 such as ethyl isobutyrate.…”