ChemInform Abstract: STEREOCHEMIE VON HETEROCYCLEN 8. MITT. SYNTH. UND EIGENSCHAFTEN EINIGER STEREOISOMERER 2,3‐DIALKYLUND 2,3‐DIALKYL‐3‐(1‐METHOXY‐AETHYL)‐OXETANE

Abstract

Die Diole (I), dargestellt durch Li‐alanat‐Reduktion geeigneter Alkylacetessigester, werden durch 24stündige Reaktion mit Acetylchlorid in Gegenwart von Ca‐chlorid bei ‐10 bis +20°C in die Chloracetate (II) (Ausbeute 76‐86%) übergeführt.

Mechanism and stereochemistry of oxetane reactions. I. Stereospecific synthesis of the diastereoisomeric 2-phenyl-3-methyloxetanes and study of their configuration and conformation by nuclear magnetic resonance spectroscopy

“…4 (3.0 g) was treated with tosyl chloride under the conditions used above to give pure G (4.3 g) as a liquid: ir 2.81 (OH), 7.40, 8.41, and 8.51 µ (OSO2-P-C7H7);29 nmr 4.20 (1 H, d, J = 8.2 Hz, CeH5CH), 4.07, 3.93 (1 H each, q, CH20), 1.97 (1 H, m, CH3CH), 0.69 ppm (3 H, d, J = 7.2 Hz, CH3CH). cjs-2-Phenyl-3-methyloxetane (7). A solution of 5 (3.90 g, 12.2 mmol) in tertbutyl alcohol (40 ml) was treated with potassium tert-butoxide (1.8 g, 16.0 mmol) and left 24 hr at room temperature.…”

“…Treatment of 5 and 6 with potassium tert-butoxide in tertbutyl alcohol at room temperature led to the diastereoisomerically pure oxetanes 7 and 8. The configurations of oxetanes 7 and 8 were Observed and calculated spectrum of cis-2-phenyl-3methyloxetane (7). Measured frequencies (in Hz) are relative to internal TMS.…”

“…Table I gives the values of the spectral parameters of 7 and 8 obtained from the above mentioned analysis. Furthermore, the corresponding data for unsubstituted oxetane 916 and 2-phenyloxetane 1012a have also been reported for the sake of comparison.…”

“…20 If one assumes that small conformational changes of the oxetane ring do not affect to a large extent the chemical shift of the oxetane protons and the substituent effects, then the evaluation of the chemical shifts through additive shielding parameters can be used with a sufficient accuracy The shielding of the 3-methyl group on cis and trans vicinal protons can be, on the Other hand, deduced by comparing the chemical shift of the Hi proton of oxetanes 8 and 10 and 7 and 10, respectively (A5(CH3 cis) = -37.1 Hz; A<5(CH3 trans) = -0.2 Hz). By adding the appropriate contribution to the chemical shift of the a protons of the unsubstituted oxetane 9, the theoretical chemical shift of H4 and H5 protons of 7 and 8 can be predicted (see Table I).…”