Reversible Grignard and organolithium reactions

Fragmentation of Homoallylic Alkoxides. Thermolysis of potassium 2‐substituted bicyclo [2.2.2]oct‐5‐en‐2‐alkoxides

“…10%) of their 2-cyclohexenyl isomers ( c j experiments [1][2][3][4][5][6]. In addition to the fact that epimeric alkoxides give the same product two observations are worthy of mention.…”

“…Thermolysis at 120" of the potassium alkoxides derived from the 2-methyl, 2-ethyl, 2-propyl and 2-isopropyl bicyclic alcohols 2-9 led to the isolation, in good yield, of the 3-cyclohexenyl ketones 18-21, together with small amounts (ca. 10%) of their 2-cyclohexenyl isomers ( c j experiments [1][2][3][4][5][6]. In addition to the fact that epimeric alkoxides give the same product two observations are worthy of mention.…”

“…This fragmentation is observed as a side reaction during the thermal rearrangement of homoallylic tertiary alkoxides (M=Li, MgCI, MgBr) [3] and in competition with the anionic oxy-Cope rearrangment (M=Na, K) [4]. Because enolatization of carbonyl groups by allylic organometallic species had never been observed, enolatization by the alkoxide substrate was considered to be more likely [3]. Only a few synthetic applications are known and involve the opening of appropriately substituted cyclobutoxides (61.…”

Pd-catalyzed nucleophilic allylic alkylation of aliphatic aldehydes by the use of allyl alcohols

“…The mixture was stirred at ambient temperature for 48 h. The mixture was washed with satd NaHCO 3 and then brine, and the organic phase was dried (MgSO 4 ) and concentrated in vacuo to give an yellow oil, which was purified by means of column chromatography over silica gel (AcOEt-hexane, 1/30 v/v) to give 1k in 78% yield. The following products were characterized by comparison of 1 H NMR spectral data with those of literature: 1-cyclohexyl-2-phenyl-3-buten-1-ol (3a), 5 1-cyclohexyl-3-buten-1-ol (3b), 5 1-(3-cyclohexenyl)-3-buten-1-ol (3c), 12 2-phenyl-5-hexen-3-ol (3g), 13 1,1-diphenyl-4-penten-2-ol (3h), 14 1-nonen-4-ol (3i), 15 6-phenyl-1-hexen-4-ol (3j), 16 7-octene-1,5-diol (3k), 6 1-cyclohexyl-2-methyl-3-buten-1-ol (3m), 16 1-cyclohexyl-3-methyl-3-buten-1-ol (3n), 17 1-cyclohexyl-2-vinyl-3-buten-1-ol (3p), 18 1-cyclohexyl-2,2-dimethyl-3-buten-1-ol (3q), 17 1-cyclohexyl-2,6-dimethyl-2-vinyl-5-hepten-1-ol (3r), 19 1-phenyl-1,5-hexadien-3-ol (3t), 20 1-phenyl-3-buten-1-ol (3u), 21 1,4-diphenyl-5-hexen-3-ol (3v), 22 3-phenyl-1-nonen-4-ol (3w), 22 (Z)-anti-2-methyl-1-phenyl-3-pentenol (3x), (E)-1-phenyl-1-penten-3-ol (5a), 5 1-phenylpropan-1-ol (5b), 21 1-(1-phenylallyl)cyclohexanol (g-7a), 21 1-(1-methylallyl)cyclohexanol (g-7b), 21 (E)-3-isopropyl-2-methyl-6-phenyl-5-hexen-3-ol (a-7f), 23 3-isopropyl-2,4-dimethyl-5-hexen-3-ol (g-7g), 23 (E)-3-isopropyl-2-methyl-5-hepten-3-ol (a-7g), 23 5-methyl-4-phenyl-1-hexen-4-ol (7h), 24 2,4-dimethyl-3-phenyl-5-hexen-3-ol (g-7j), 23 1,1-diphenyl-3-buten-1-ol (7k). 25 4.2.…”

Rearrangement and Substitution of Pentadienyl Groups in Homopentadienylamines on Treatment with Organolithium Reagents

“…This has been demonstrated, for example, by the isomerization of the branched homoallylic compounds to the linear ones (route A in Scheme 1) on increasing the reaction time before quenching the organometallic reactions. Scheme 1 The rate of the retro-allylmetallation is affected by steric hindrance in the homoallylic alkoxides or amides and by the nature of the metal, decreasing in the order: ZnX Ͼ Li Ͼ MgX for alkoxides, [5,7,8] and Li Ͼ ZnX Ͼ MgX for amides. [9,10] Moreover, electron-withdrawing substituents on the allyl group facilitate the retro-allylmetallation: pentadienyl-and cinnamyllithium and -zinc bromide are known to add reversibly to carbonyl compounds, differing in this respect from 2-pentenyland 3,3-dimethylallyllithium.…”