Synthesis of 1‐Bicyclo [3.2.2]nonene and 1 (7)‐Bicyclo [3.2.2]nonene by Intramolecular Wittig Reaction

Abstract

The synthesis of 1‐bicyclo[3.2.2]nonene (2) and of 1 (7)‐bicyclo [3.2.2]nonene (3), two isomeric bridged (E)‐cycloheptenes, by intramolecular Wittig reaction is described. These ‘Bredt olefins’ could not be isolated, but dimerized rapidly. In both cases, the main product was shown to be a head‐to‐tail dimer with a cyclobutane ring. The ‘Bredt olefins’ were also trapped in situ with furan or 2,5‐diphenylbenzo [c]furan.

Synthesis of β-, γ-, δ-, ..., ω-Halogenated Ketones and Aldehydes

“…As stated in the previous sections, esters of sulfonic acids are good leaving groups. Hence, alcohols are often activated toward nucleophilic substitutions by converting them into mesylates (Scheme ) . In a typical procedure, the alcohol is treated with mesyl chloride 55 in dry CH 2 Cl 2 , , in the presence of a base such as Et 3 N, at room temperature or below.…”

“…Hence, alcohols are often activated toward nucleophilic substitutions by converting them into mesylates (Scheme ) . In a typical procedure, the alcohol is treated with mesyl chloride 55 in dry CH 2 Cl 2 , , in the presence of a base such as Et 3 N, at room temperature or below. This transformation usually proceeds in very high yield, if not quantitative.…”

“…This transformation usually proceeds in very high yield, if not quantitative. Subsequently, the mesylate 1143 is treated with LiCl or LiBr in warm acetone to furnish the respective alkyl halide 1144 . ,, In some cases, the halogenation step is performed in the presence of the sodium salt of the halide , or in another polar aprotic solvent such as DMF . The example presented in Scheme illustrates the possible occurrence of acetal hydrolysis under the conditions used to substitute the mesylate for a halide.…”

[2 + 2]‐Cycloadditions to Strained Bridgehead Olefins. I. 1, 1‐Dichloro‐2,2‐difluoroethene

“…These so-called Bredt olefins [ 11 formally are methylene-bridged (E)-cyclooctenes [2] and therefore should be comparable in strain and reactivity to the model compound (E)-1-methylcyclooctene (4). Their high reactivity has been documented by a number of additions which are not observed with unstrained alkyl-substituted olefins [3].Bredt olefins belonging to the class of bridged (E)-cycloheptenes or (E)-cyclohexenes are unstable at ordinary temperatures and usually dimerize to mixtures of cyclobutanes by a [2+2]-cycloaddition [4]. It is therefore of interest to study [2 + 21-cycloadditions of the stable bridged (E)-cyclooctenes 1, 2, and 3, and compare these with more and with less strained olefins.…”

“…Bredt olefins belonging to the class of bridged (E)-cycloheptenes or (E)-cyclohexenes are unstable at ordinary temperatures and usually dimerize to mixtures of cyclobutanes by a [2+2]-cycloaddition [4]. It is therefore of interest to study [2 + 21-cycloadditions of the stable bridged (E)-cyclooctenes 1, 2, and 3, and compare these with more and with less strained olefins.…”