565-78-6Relevant articles and documents
On rearrangements by cyclialkylations of arylpentanols to 2,3-dihydro-1H-indene derivatives. Part 5. The acid-catalyzed cyclialkylation of 2-(2-chlorophenyl)-2,4-dimethylpentan-3-ol
Fathi, Behrouz,Giovannini, Edgardo,Pasquier, Pierre
, p. 2089 - 2104 (2007/10/03)
The mechanism proposed in [1] to explain the surprising result of the cyclialkylation of 4-(2-chlorophenyl)- 2,4-dimethylpentan-2-ol (3, R = Me), which gives not only the 'normal' product, i.e., the 4-chloro-2,3-dihydro-1,1,3,3-tetramethyl- (4), but also the isomer trans-4-chloro-2,3-dihydro-1,1,2,3-tetramethyl-1H-inden (5), could be differentiated in two sections (cf. Scheme 2): the first from 3 to the intermediary ion IIa?IIb, and the second from the latter ions to the final product 5. For the first section, a sufficiently satisfactory explanation has been given in [1]; the second section has received important support from the mechanisms of the cyclialkylation of 2,4-dimethyl-2-phenylpentan-3-ol (6), the precursor of II′a, the ion IIa without the o-Cl substituent (cf. Schemes 2, 3 and 5 and [4]). The present communication gives an explanation of the influence of the o-Cl substituent: a mechanism is proposed for the very complex cyclialkylation of 2-(2-chlorophenyl)-2,4-dimethylpentan-3-ol (11; cf. Scheme 9). Both mechanism may be considered as definitive. It is very surprising that, by the cyclialkylation of the compounds 1, 3, 8, 11, 15, and 17, only compound 1 gives the 'normal' product: the cyclialkylation of all other phenylpentanols follows complex pathways including Et, i-Pr, and Ph migrations, which could not be expected. In addition, it has been established that the transformation of 21 to 22 (cf. Scheme 12) and that of 23 to 24 (cf. Scheme 13) occur through two consecutive 1,2- and not through a single 1,3-hydride migration or through an elimination-addition process (cf. Scheme 13). It can be assumed that the transformation of ion IV (the 2-(2-chlorophenyl)-3,4-dimethylpent-2-ylium ion) to the ion V (the 4-(2-chlorophenyl)-3,4-dimethylpent-2-ylium ion (both shown in Scheme 9 as D-isomers) occurs through the same pathway.
Charge-reversal Mass Spectra of Enolate Ions of Some Open-chain and Cyclic Ketones for Structure Identification
Suerig, Thomas,Gruetzmacher, Hans-Friedrich
, p. 446 - 452 (2007/10/02)
The charge-reversal (CR) mass spectra of the enolate ions of heptanal and ten isomeric heptanones, of cyclohexanone, of cycloheptanone, of isomeric methylcyclohexanones, of isomeric ethylcyclohexanones and of the isomeric monoterpene ketones camphor, fenchone, pulegone and thujone were obtained by deprotonating using OH(-) under chemical ionization conditions followed by collision of the (-) ions with helium in the second field-free region of a VG ZAB 2F mass spectrometer.The CR mass spectra were evaluated by similarity index (SI) values.Characteristic of the CR mass spectra of the open-chain enolates are fragment ions formed by α- cleavage.However, the CR mass spectra are dominated by peaks of small hydrocarbon ions, particularly in the case of cyclic and bicyclic enolates.The CR mass spectra of enolates of linear heptanones differing in the position of the carbonyl group can be easily correlated with the structure of the parent ketone.The CR mass spectra of enolates of isomeric heptan-2-ones differing only in the degree of branching of the alkyl group are similar, but can be distinguished by the SI values.The CR mass spectra of the enolates of the isomeric cyclic and bicyclic ketones studied are more or less identical and cannot be used for structural assignment.
