Steric crowding in organic chemistry. VI. Reactivity of tri-tert-butylethylene and related compounds

Abstract

icals have, in fact, been photolytically generated from secondary amines in strongly acidic media.16 Parallelling our present results, spontaneous production of aminium radicals from protonated chloramines under mild conditions was observed,16 and subsequent fast addition to unsaturated hydrocarbons. If ordinary aliphatic aminium radicals are generated in weakly basic, neutral, or weakly acidic aqueous media, we have found,17 rapid loss of a protons occurs with subsequent oxidative dealkylation. Hence, the characteristic reactions of aminium ions near neutrality are different from those in strongly acidic media. Experimental SectionWater and triethylenediamine perchlorate were purified as previously described.1 Aqueous hypochlorous acid solutions (16) W.

Vinyl ether hydrolysis. XV. Methyl β,β-di-tert-butylvinyl ether: buttressing steric effects

“…Highly congested systems such as that investigated here are prone to rearrangement; this is especially likely if their reactions produce cations which can be transformed to more stable species (4,5,15). The ion produced by straightforward protonation of the P-carbon of the present substrate is an alkoxy substituted cation stabilized by resonance (eq.…”

“…The ion produced by straightforward protonation of the P-carbon of the present substrate is an alkoxy substituted cation stabilized by resonance (eq. [5]); its rearrangement is therefore apt to be an…”

“…of two tert-butyl groups at the reaction site might also impede approach of the electrophilic reagent (H+); tri-tert-butylethylene is known to add bromine only slowly because of steric hindrance (5). These effects would serve to produce a rate retardation greater than the product of the retardations shown by the cis and trans monosubstituted substrates separately, rather than the less than cumulative retardation actually observed.…”

Biogenetic-Type Rearrangements of Terpenes

“…A study of the effect of solvent upon the products resulting from deamination of isobutyl amine indicates that cyclopropane formation is enhanced in non-polar solvents (182). 1,3-hydrogen elimination to cyclopropanes has also been found in the solvolysis (183) and pyrolysis (184) of highly hindered p-nitrobenzoates. …”

“…Since (X-bulnesene is itself regarded as being formed by a proton-induced cyclization of germacratriene (see section C.2 above), the overall conversion of farnesyl pyrophosphate to the patchoulanes is rather unusual in necessarily proceeding via two deprotonated intermediates. The closely related isopatchoulane sesquiterpene cyperene (184) and its relatives are presumably formed similarly by a protonation-cyclization Operation upon 1 0-epi-(X-guaiene having the C10 methyl group in the unusual (X-configuration. The seychellane sesquiterpenes result from yet another rearrangement, a 1 ,2-methyl migration in the bridgehead carbonium ion (181) and subsequent proton elimination.…”