38445-62-4Relevant articles and documents
Molybdenum(II)- and tungsten(II)-catalyzed allylic substitution
Malkov, Andrei V.,Baxendale, Ian R.,Dvorak, Dalimil,Mansfield, Darren J.,Kocovsky, Pavel
, p. 2737 - 2750 (2007/10/03)
The molybdenum(II) complexes Mo(CO)5(OTf)2 (7a), [Mo(CO)4Br2]2 (8a), their tungsten(II) congeners 7b and 8b, and bimetallic complex Mo(CO)3(MeCN)2(SnCl3)Cl (9a) have been found to catalyze the C-C bond-forming allylic substitution with silyl enol ethers derived from β-dicarbonyls (e.g., 16 + 30 → 46) or from simple ketones (e.g., 16 + 32 → 50), aldehydes, and esters as nucleophiles under mild conditions (room temperature, 1-2 h). Methanol, as a prototype oxygen nucleophile, reacts in a similar fashion (e.g., 16 + MeOH → 43). Mechanistic and stereochemical experiments are indicative of Lewis-acid catalysis rather than a metal template-controlled process.
The reaction of cyclic allylic alcohols with aliphatic alcohols in the presence of cerium(III) chloride
Uzarewicz,Dresler
, p. 181 - 195 (2007/10/03)
Cyclic secondary and tertiary allylic alcohols react with primary aliphatic alcohols in the presence of cerium(III) chloride heptahydrate to give alkyl allylic ethers. When secondary or tertiary aliphatic alcohols are used 1,3-dienes are obtained from allylic alcohols heaving the 3-methyl-2-en-1-ol moiety (3-8, 13-15).
Regioselectivity in the gas - phase nucleophilic attack on O - protonated 3-methyl-2-cyclohexen-1-ol and 1-methyl-2-cyclohexen-1-ol
Dezi, Emanuela,Lombardozzi, Antonietta,Renzi, Gabriele,Pizzabiocca, Adriano,Speranza, Maurizio
, p. 323 - 334 (2007/10/03)
Our radiolytic study of the occurrence in the gas phase of concerted SN2' reactions on several open-chain allylic oxonium ions generated in the gas phase from the attack of gaseous GA+ acids (GA+ = CnH+5 (n = 1, 2), iC3H+7, and (CH3)2F+) on suitable substrates is now continued with cyclic allylic alcohols, such as 3-methyl-2-cyclohexen-1-ol (1) and 1-methyl-2-cyclohexen-1-ol (2), with both MeOH and NMe3 as neutral nucleophiles.With MeOH as the nucleophile, the substitution reaction exclusively takes place on 1 as the starting compound, whereas when the substrate is 2 it is accompanied by extensive elimination.With NMe3, only the elimination reaction is observed in the same systems.The analysis of the isomeric distribution of the substitution and elimination products allows definition of the corresponding reaction patterns.As for open-chain oxonium ions, the nucleophilic attack on O-protonated 1 and 2 is preceded by significant intramolecular interconversion.Partial unimolecular dissociation of the same ionic intermediates also takes place.After careful evaluation of the extent of these side processes, it is demonstrated that the O-protonated 1 undergoes the concerted SN2 process with MeOH almost exclusively ( 99percent).With O-protonated 2, however, the concerted SN2' pathway (84-95percent) prevails over the classical SN2 one (6-17percent).Concomitant (E2) and elimination (E2') pathways involve attack of the selected nucleophiles on the oxonium ions from 1 and 2.Their relative extent (E2'/E2:1.78-1.96 (1); 1.43-1.70 (2)) appears only slightly dependent on the nature of the ionic substrate, the nucleophile (whether MeOH or NMe3), and the leaving group (whether H2O or MeOH).The effects of both intrinsic structural factors and experimental conditions in determining the SN2'/SN2 and E2'/E2 branchings in the selected oxonium ions is discussed and compared with related gas-phase data. - Keywords: cyclohexenols; elimination reactions; gas-phase chemistry; mechanistic studies; nucleophilic substitutions
