639. The rearrangement of αβ-unsaturated alcohols to saturated aldehydes and ketones. Part II. The course of the rearrangement

Abstract

The rates of change of a number of +unsaturated alcohols into carbonyl compounds are compared with those of the corresponding 1 : 2-glycols, and a hypothesis to account for the observed results is developed.IN order to follow the change of an unsaturated alcohol or a 1 : 2-diol into a carbonyl compound a rapid and reliable method of estimating aldehydes and ketones in dilute solution was necessary. Several methods were tested against isobutyraldehyde and methyl isopropyl ketone. 2 : 4-Dinitrophenylhydrazine or dimedone did not give reproducible results. Modifications of Ripper's bisulphite method and of Romijn's alkaline iodine method were also unsuitable. Accurate and reliable results were obtained with the silver oxide method6 but it was time-consuming. Eventually a colorimetric method based on the use of Schiff's reagent was adopted for the estimation of aldehydes. For ketones, Mitchell and Smith's hydroxylamine method proved satisfactory provided that comparison was made with reference samples.The rates of change of 2-methylprop-2-en-1-01 and of 2-methylpropane-1 : 2-diol into isobutyraldehyde in presence of sulphuric acid were determined in water-dioxan (3 : 1 v/v), at 90" 5 0.1". The observed values of k, the first-order rate constant, are shown in Table 1.The rearrangements of unsaturated alcohol and the glycol are obviousIy both first-order * Part I, preceding paper.

Characterization and synthesis of volatile compounds from the defensive secretions of some "daddy longlets" (Arachnida: Opiliones: Leiobunum spp.).

“…Ethyl a-diethylphosphonopropionate (7) (23.8 g, 0.1 mol) was added over i hr to a stirred suspension of 2.4 g of sodium hydride in 35 ml of benzene carefully maintained at 20°under nitrogen. After stirring an additional hour we added 8.4 g (0.1 mol) of tiglic aldehyde (8) dropwise over a 15-min interval while the temperature of the mixture was maintained at 25°. The mixture was refluxed for 15 min, and then the benzene layer was decanted.…”

Generation and Electrophile Trapping of N-Boc-2-lithio-2-azetine: Synthesis of 2-Substituted 2-Azetines

“…Observations with two electrophiles (pivalaldehyde and diphenyl disulfide) show further reactivity following electrophile trapping. While the hindered alcohol 6d derived from pivalaldehyde could be isolated in good yield as indicated (84%, Table , entry 4), exposure to CDCl 3 which had not been passed through alumina prior to use resulted in prototropy driven by relief of strain, to the corresponding saturated ketone 8 (57%, Scheme ); other aldehyde-derived adducts did not undergo analogous isomerizations.…”

The Heck-type arylation of allylic alcohols with arenediazonium salts

“…3-Methylbut-3-en-2-ol [12], 2,5-dimethylhex-1-en-3-ol [13] and Pd(dba) 2 [14] were prepared according to reported procedures. 1 H and 13 C NMR (250 and 62.5 MHz or 200 and 50 MHz) spectra were obtained on Bruker AC spectrometers using TMS as internal standard and CDCl 3 as solvent.…”