Vernon G. S. Box

The Role of Lone Pair Interactions in the Chemistry of the Monosacceharides. The Aromatic Effects

The electronic factors which contribute to the anomeric effects have been attributed to the destabilizing n-n (lone pair-lone pair), or/and the stabilizing n-σ * , interactions of the non-bonded electron pairs of geminal heteroatoms. Predictions of the chemistry of the simple monosaccharide acetals, based on a n-σ * hypothesis, are not consistent with the experimentally observed chemistry. Thus, the n-σ * hypothesis is not a useful model for rationalizing the chemical reactivity of acetals, or the closely related anomeric effects. A study of the X-ray crystallographic data of some monosaccharides also casts considerable doubt on the validity of the bond length and bond angle criteria that have been used to assert the importance of the n-σ * hypothesis. A hypothesis based on dominant n-n interaction, with a minor contribution from the n-σ * interactions, is a better model for rationalizing the chemistry of the simple acetals. This combination of electronic factors illuminates both the anomeric effects and the chemistry of the acetals

The Synthesis of b-Lactones and b-Lactams from Malonates and Malonamides

The rhodium diacetate induced insertion reactions of some simples esters and amides of diazomalonic acid result in the formation of β-lactones and β-lactams

The role of lone pair interactions in the chemistry of the monosaccharides. Stereo-electronic effects in unsaturated monosaccharides

The X-ray crystallopraphic structural data for simple unsaturated monosaccharides do not support the participation of the electron density of a C2-C3 π bond in the modification of the geometry at the anomeric center, or the existence of a vinylogous anomeric effect in glycals. The delocalization phenomena (n-σ*, n-π* and π-σ*) are insignificant in the ground states of the simple sugars, and n-n repulsions are the dominant stereo-electronic effects in these molecules

The selective benzylic bromination of o-xylenes. A useful synthesis of phthalides

The free radical bromination of aryl methyl groups can be controlled by the strategic positioning of a remote stereo-electronic blocking group on the aryl ring. This tactic leads to the efficient synthesis of selectively benzylically brominated molecules which are useful synthetic intermediates. This methodology has been applied to the synthesis of some phthalides

Enantio-eudesmane sesquiterpenes from it Verbesina rupestris

Abstract The leaves and stems of Verbesina rupestris contain enantio-eudesmane sesquiterpenes, isolated as esters of cinnamic acid. This finding supports th

The relationship between bond type, bond order and bond lengths. A re-evaluation of the aromaticity of some heterocyclic molecules

Radical nucleophilic carbamoylation was carried out to various 1,2,3-triazine derivatives. In the case of parent triazines as substrates, Miniscis system was not effective, and in the absence of acid, a small amount of radical adduct was obtained. Triazinium dicyanomethylides reacted with carbamoyl radical to give 5-carbamoyltriazines in good yields. Other 1,2,3-triazine derivatives were also investigated

The significance of the bond lengths and bond orders of conjugated unsaturated organic molecules. The role of hetero-aromaticity in the tertiary structures of DNA

New criteria (based on X-ray crystallographic data) for assessing the presence of delocalization in conjugated π systems reveal that delocalization is not a widespread phenomenon in the ground states of many of these π systems. Instead, these molecules prefer to retain highly localized, independent, π systems. Thus, many explanations of the structural features and reactivities of these unsaturated organic molecules, based on their presumed delocalized ground states, must be critically reviewed. This is especially important for understanding the chemistry and properties of hetero-aromatic molecules

The syntheses of some methyl 3-C-alkyl-2,3-dideoxy-α-d-glycero-hex-2-enopyranosid-4-uloses

Abstract A general synthetic route to the title compounds is outlined which involves: ( a ) the Grignard reduction of methyl 2- O -benzoyl-4,6- O -benzylidene-α- d - ribo -hexopyranosid-3-ulose; ( b ) the dehydration of the derived methyl 2- O -acetyl-3- C -alkyl-4,6- O -benzylidene-α- d -allopyranoside, with thionyl chloride-pyridine, at 0°, to provide the methyl 2- O -acetyl-3- C -alkyl-4,6- O -benzylidene-3-deoxy-α- d - erythro -hex-3-enopyranoside; and finally ( c ) the acid-catalyzed fragmentation of the alkene to the title compounds. Synthetic routes from the title compounds to some novel branched-chain sugars and some rotenoids are proposed.

The role of oxygen substituents in the elimination and enolisation reactions of 4,6-O-benzylidene-hexopyranosides and -hexopyranosiduloses

Abstract An attempt is made to rationalise the elimination and enolisation processes observed in 4,6-O-benzylidenehexopyranosides and hexopyranosiduloses. The roles of the oxygen substituents on the pyran ring are outlined, and it is suggested that these oxygen atoms control the paths of the reactions.

The birch reduction/alkylation of phthalides the synthesis of some substituted bicyclo[3.2.1.]octanes

The first successful reductions of the aromatic rings of phthalides, with the preservation of the lactone rings, are reported. The reduction/alkylation of some substituted 4-methoxyphthalides gave lactonic enol ethers, which were converted into conjugated homocyclic dienes and further into cyclohexenones. These enones were easily converted into bicyclo[3.2.1]octanes by the Bu 3 SnH/AIBn free radical cyclization reaction