Γ-Lakton-cis-anellierung an Δ2- und Δ3- Cholesten

γ-Lactone-cis-annulation to Δ²- and Δ³- Cholestene. From Δ²- and Δ³- cholestene the γ-lactones 11a , 11b , 12a , and 12b are synthesized through the dibromocarbene adducts 3 and 4 , the bromohydrines 5 and 6 , the oxapiropentanes 7 and 8 , and the cyclobutanones 9a , 9b and 10a , 10b , respectively. The ¹³C-NMR.-spectra of 1–8 and 11 as well as the ORD.-spectra of the cyclobutanones 9 and 10 are reported.     

Determination of ΔH≠ and ΔS≠ by simultaneous 1H and 13C dynamic n.m.r. studies: Importance of the accuracy of temperature measurement

From ΔG_Tc^≠ values obtained by ¹H and ¹³C dynamic nuclear magnetic resonance studies of the same dynamic process, it is possible to estimate ΔH^≠ and ΔS^≠. Nevertheless, the accuracy of the temperature measurement is a factor which limits the applicability of this method. A very simple procedure for calibrating the usual temperature sensors is described, which can be applied to all types of n.m.r. probes. By the use of this procedure it is possible to measure coalescence temperatures in ¹H and ¹³C n.m.r. with such an accuracy that ΔS^≠ can be effectively determined from the difference between ΔG_Tc^≠ values.     

NMR spectra of Δ3- and Δ4-pyrrolin-2-one

The spectra of Δ³- and Δ⁴-pyrrolin-2-one were analysed and the sign of all the coupling constants determined by tickling and triple resonance experiments. A positive allylic interaction (J_xz in 2 ) is reported and four-bond couplings are discussed in particular. Deuterium exchange affords evidence for the tautomeric equilibrium between 1 and 2 .     

Δ3- and Δ4-1,2,4-oxadiazolin-5- and 3-ones

Preparations for 2,3-diphenyl- and 2-benzyI-3-phenyl-Δ³-1,2,4-oxadiazolin-5-ones (3) and (4) and for 2,5-diphenyl-Δ⁴-1,2,4-oxadiazolin-3-one ( 7 ) are reported.     

Umsetzungen von Δ-triazolinen und von ringketon-anilen mit isocyanaten und isothiocyanaten

Δ²-Triazolines, derived from cyclopentene and aryl azides, react with isocyanates and isothiocyanates giving 1-arylamino-2-carboxamido- and 1-arylamino-2-thiocarboxamido-cyclopentenes respectively. Cyclopentanone anils, which are formed from the triazolines by thermal loss of nitrogen, are intermediates. In contrast, the Δ²-triazoline from norbornene and phenyl azide undergoes induced loss of nitrogen on treatment with phenylisocyanate. The product, a 1:1 adduct less N₂, has been investigated chemically and spectroscopically; the final structural elucidation however requires further experiments.     

Synthese und reduktive Cyclisierung eines Δ18-Dehydro-A/D-secocorrinkomplexes

A Δ¹⁸-dehydro-A/D-secocorrin complex has been synthesized and shown to cyclize smoothly to the corresponding corrin complex by electrochemical reduction in a protonating medium. The crucial step of the construction of the secocorrinoid substrate illustrates a novel variant of the Bamford-Stevens reaction.     

Photochemische Reaktionen. 34. Mitteilung. Die Photoisomerisierung von 3-Oxo-Δ1;4-Steroiden in Dioxanlösung. 3,11-Dioxo-17β-acetoxy-Δ1;4-androstadien und 3-Oxo-17β-acetoxy-Δ1;4;9,11-androstatrien

Ultraviolet irradiation of the steroidal cross-conjugated dienones 3 and 7 , and of the bicyclohexenone derivative 16 in dioxane solution produced the virtually quantitative isomerizations 3 → 11 (Chart 3) and 7 → 16 → 17 (Chart 6). These conversions are consistent with the previously established general scheme a → b → c → d → e (Chart 1). By analogy with these results, it is suggested that the photo-isomers 9 and 10 of O-acetylprednisone ( 8 ) represent products resulting from multiple photorearrangements rather than from direct transformations, as had been proposed in the literature.     

Benzomorphan related compounds. III.. Structural determination of Δ3 - and Δ4-tetrahydropyridines by nuclear magnetic resonance

Observation of the nmr spectra of several Δ³ - and Δ⁴-tetrahydropyridines hydrochlorides provides a useful method for the structural determination of this type of compound. The Δ³ - Isomers exist as one predominant epimer only whereas the Δ⁴-isomers exist as a mixture of the two possible epimers. The respective assignments are discussed in view of the criteria previously applied in the study of this type of compound.     

Synthese von 5-Methyl-3-oxa-A-nor-5β-cholestan und 3-Oxa-Δ4-cholesten-2-on

2, 3-seco-Δ⁴-Cholestene-2, 3-dicarboxylic acid ( 5 ) was prepared in 30% yield from 2-hydroxymethylene-Δ⁴-cholestene-3-one ( 1 ) by ozonolysis under special conditions. Pyrolysis of the pure di-acid 5 gave A-nor-Δ³⁽⁵⁾-cholestene-2-one ( 6 ), the anhydride 2 and 5-methyl-3-oxa-A-nor-5β-cholestane-2-one ( 8 ). Pyrolysis of amorphous acidic material obtained by the ozonolysis of 1 yielded the enol-lactones 7 and 9 as additional products. LiA1H₄-reduction of the γ-lactone 8 gave the diol 10 , which was transformed into 5-methyl-3-oxa-A-nor-5β-cholestane ( 13 ) by treatment with tosyl chloride in pyridine.     

Addition-rearrangement reactions of 5-amino-3-oxo-Δ4–1,2,4-thiadiazolines

Bond-switching rearrangement via hypervalent sulfur occurs during the reactions of 5-anilino-2-benzyl-3-oxo-Δ⁴–1,2,4-thiadiazoline 5 with electrophilic nitriles, isothiocyanates, carbon disulfide and ketenes, yielding the products 6 and 7. In contrast, N,N'-ditolylcarbodiimide reacts with 5 to give the normal addition product 8 , which rearranges only partially to 9 in several solvents (chloroform, acetonitrile and dimethyl sulfoxide). The equilibrium position depends on the temperature, favoring 9 at higher temperatures.