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A new chiral auxiliary, non-cross-linked polystyrene-supported oxazolidine-2-selone was synthesized using N-Boc-l-tyrosine ethyl ester as starting material. The structure of the target product was detected by IR, NMR, elemental analysis, and the spectrum result was consistent with the molecular structure.

A series of oxazolidin-2-ylidenes and one tetrahydro-1,3-oxazin-2-ylidene, generated by thermolysis of Δ3-1,3,4-oxadiazolines in benzene at 90 °C, were intercepted by insertion into the OH bond of phenols. In two cases the initial products rearranged to N-(2-aryloxyethyl)-N-methylformamides. The activation energy for rotation about the amide CN bond of those ultimate products was measured as 20.4 kcal/mol. The aminooxycarbenes reacted with two equivalents of methyl or phenyl isocyanate to give spiro-fused hydantoins. Major products from the reactions of the N-carbonyl carbenes with dimethyl acetylenedicarboxylate or with methyl propiolate were 2-oxazolines resulting from apparent acyl transfers from N to C in the proposed dipolar intermediates; minor products of 1:2 (carbene:trap) stoichiometry were also observed. Keywords: nucleophilic carbene, aminooxycarbene, oxadiazoline, amide rotation, oxazolidine.

Δ3-1,3,4-Oxadiazolines spiro-fused at C2 to C2 to oxazolidines (12) or to C2 of tetrahydro-1,3-oxazines (13) were synthesized. The oxadiazolines undergo thermolysis in benzene at 90 °C with first-order rate constants of (1.6–50) × 10−5 s−1. The dependence of these rate constants on the nature of the substituents present on the oxadiazoline ring is consistent with a mechanism involving a carbonyl ylide intermediate. Substituents on N of the oxazolidine or tetrahydro-1,3-oxazine moieties play a major role in determining the fragmentation pathways. Oxadiazolines with N-carbonyl groups (12c–j, 13d,e) afford essentially quantitative yields of the corresponding aminooxycarbenes, while other fragmentation reactions compete with carbene generation in the case of oxadiazolines with N-methyl (12b, 13c) or N-sulfonyl (12k) groups. Keywords: nucleophilic carbene, aminooxycarbene, oxadiazoline, oxazolidin-2-ylidene, carbonyl ylide.

A series of monopiperidine, 1, dipiperidine 2, 3 (syn and and), as well as the corresponding oxazoline and oxazolidine crown ethers have been prepared and their ionophoric properties evaluated. The syn-dipiperidine 2c turned out to be a particularly efficient Ca2+ ligand (log K = 9.7). 13C and 23Na nuclear magnetic resonance spectroscopy was used to evaluate the nature of the complex between the monopiperidine 1c, the syn-dipiperidine 2c, and Ca2+ and Na+ ions. In methanol–water solution, the dimeric salt (2c)2Ca exhibits both a tight or asymmetric and a symmetric or loose ion pair between the cation and the carboxylate groups. Sodium-23 chemical shifts and line-width variation both support a 1:1 complex with 1c and 2c. The structural results correlate with observations from ion transport experiments.

Preparative-scale high pressure liquid chromatography on 3-acetyl-2-(2′,6′-dimethyl-5′-heptenyl)oxazolidine (1), a complex acetamide derivative of citronellal, resulted in isolation of the diastereomeric forms of this insect repellent. The two diastereomers were designated as 1a and 1b on the basis of their order of elution from silica gel and from a variety of capillary gas chromatography columns. Interpretation of the 13C nuclear magnetic resonance spectra of 1a and 1b was accomplished by comparison with model compounds and by off-resonance proton-decoupling experiments. Absolute stereochemical assignments were not made. Because of the amide group, the diastereomers existed in solution at ambient temperature as cis and trans rotational isomers, which caused nonequivalence of most of the carbon atoms, including the olefinic carbons at C-5′ and C-6′. trans Isomer (5) was concluded to be the major contributor to the rotational equilibrium. The spectrum of 3-acetyl-2-(4′-methyl-3′-pentenyl)oxazolidine (7) was also recorded for comparison.

Reactions of the oxazolidine (2) and thiazolidine (3) derivatives of 2-mesyloxymethylglyceraldehyde acetonide with oxygen and sulphur anions are described. Whereas oxazolidine formation does not protect the aldehyde function against nucleophilic attack, the thiazolidine group is completely inert to these nucleophiles.

The action of thionyl chloride followed by an alkaline work-up quantitatively isomerizes trans-1,2-dibenzoyl-1-(2-hydroxylcyclopentyl)hydrazine(5) to cis-2-benzoyl-1-(2-benzoyloxycyclopentyl)hydrazine (3). One equivalent of tosyl chloride in pyridine converts 5 to an intermediate which can be hydrolyzed to a mixture of 3 and 5 or can be transformed to the N-tosyl derivative 13 by tosylation and then hydrolysis. Oxazolidine structures are suggested as intermediates for these reactions.The alcohol 2 can also be isomerized to 3, using 0.8 N aqueous ethanolic hydrochloric acid, to which 5 is inert. The ester 3 is again the major product in the hydrolysis by this acid mixture of the cis-tribenzoyl derivative 17, the cis-N1-p-anisoyl derivative 21a and the cis-N1-acetyl derivative 21b, the amide group being cleaved much more rapidly than the ester, especially in the case of 21b. A mechanism involving ester participation by way of an oxazolidinium cation is proposed for these amide hydrolyses, and this is supported by tracer studies.The trans-esters 24a and b hydrolyze mainly at the ester group with retention of configuration.Polymorphism is a common phenomenon among the title compounds.

Starting from mannitol diacetonide, a simple, high yield preparation of the title compounds is described.