Semiempirical and ab initio molecular orbital studies on the mechanism of the acid-catalyzed isomerization benzene oxide .fwdarw. phenol. 1. Structure of protonated benzene oxide

Valence isomerization of cyclohepta-1,3,5-triene and its heteroelement analogues

The valence isomerization of the all-carbon and heteroelement analogues of cyclohepta-1,3,5-triene into the corresponding bicyclo[4.1.0]hepta-2,4-dienes is reviewed to show the impact of the heteroatom on the stability of both valence isomers. The focus is on the parent systems and their synthetic applications.

Asymmetric hydroxylative phenol dearomatization through in situ generation of iodanes from chiral iodoarenes and m-CPBA

'I' is all the hype: A twofold excess of iodoarene in the title reaction leads to ortho-quinols in good yields, whereas organocatalytic versions of this reaction enable subsequent epoxidation in a regio- and diastereoselective fashion. Chiral iodobiarenes led to enantioselectivities up to 50 % ee. m-CPBA = meta-chloroperoxybenzoic acid.

Density functional theory study of the mechanism of the BF(3)-catalyzed rearrangement of 2,3,3-trimethyl-1,2-epoxybutane to 2,3,3-trimethylbutanal

The potential energy surface for the rearrangement of BF(3)-coordinated 2,3,3-trimethyl-1,2-epoxybutane to 2,3, 3-trimethylbutanal has been investigated at the B3LYP/6-31G level of theory. SCRF(SCI-PCM) solvent calculations and theoretical primary and secondary kinetic isotope effects at the same level of theory provide support for a two-step process with ring opening of the BF(3)-coordinated epoxide to a tertiary carbocation intermediate followed by hydride/deuteride migration to give aldehyde. The experimentally measured primary isotope effect (k(H)(D)/k(D)(H)) requires a correction for an appropriate secondary isotope effect to give a true isotope effect k(H)(H)/k(D)(H). For the lowest energy pathway for hydride migration, the calculated secondary kinetic isotope effect is 0.92, which when applied to the experimentally measured isotope effect of k(H)(D)/k(D)(H) = 1.73 gives a revised "true" primary kinetic isotope effect of k(H)(H)/k(D)(H) = 1.59. This compares with a calculated value of 2.01. From intermediate 15, migration of the C1-H(a) proton via 19 is energetically favored over C1-H(b) migration via 18 and this result is consistent with the experimental results in which hydride migration of the proton cis to the methyl is favored.