A novel cycloaddition reaction of p-benzoquinones. Transannular cycloaddition in p-C8-bridged p-benzoquinones by way of an oxyallyl intermediate

The transannular cycloaddition between the double bond on the side chain and the $\text{p}$-benzoquinone ring in $\text{p}$-C₈-bridged $\text{p}$-benzo-quinones by way of an oxyallyl intermediate is described.     

The ipso-nitration of p-cresol

The nitration of $\text{p}$-cresol by nitric acid in aqueous sulphuric acid involves ~40% $\text{ipso}$-substitution at C^Me. The 4-methyl-4-nitrocyclohexa-2,5-dien-1-one (I) formed undergoes an acid-catalysed rearrangement to 4-methyl-2-nitrophenol.     

Behavior of p-dimethylamino-α-bormostyrene and its dimer in dioxane-water

Monomeric $\text{p}$-dimethylamino-$\text{α}$-bromostyrene undergoes S_Nl increasingly slowly in 60 to 91% dioxane. Reaction is catalyzed by HClO₄, NaOH and NaClO₄. Dimer 11 reverts to monomer I in 91% dioxane. There is only a small solvent effect on the solvolysis rate of II.     

Solvolytic behavior of p-dimethylamino-α-bromostyrene in water solutions

Nmr and UV studies show that $\text{p}$-dimethylamino-$\text{α}$-bromostyrene, I, undergoes S_Nl reaction in H₂O and HClO₄ (^kS_Nl = 6 × 10^?1sec.^?1 at 25°). The vinyl cation has an extraordinary selectivity for capture by aromatic amines relative to H₂O, including I itself to give the dimer II.     

Stereoselective photosolvolyses of ipso-acetoxynitro-adducts of p-xylene

Diastereoisomers of 1,4-dimethyl-4-nitro-2,5-cyclohexadienyl acetate exchanged acetoxyls for alkoxyls on irradiation in alcohols to give the diastereoisomers of alkyl, 1,4-dimethyl-4-nitro-2,5-cyclohexadienyl ethers in isomer ratios of 70:30, whereas the irradiation in pentane yielded $\text{p}$-xylene.     

Pyridinium p-toluenesulfonylmethylide as a formyl anion equivalent

Pyridinium $\text{p}$-toluenesulfonylmethylide serves as a formyl anion equivalent and, in the presence of an alcohol, undergoes 1,4-addition to $\text{N}$-substituted maleimides to give alkoxy- (or aryloxy)-methylene-succinimides. The protected aldehyde group can be liberated readily.     

Reaction of superoxo Co(III) complexes with 2,6-di-t-butyl-p-benzoquinone methides

Superoxo Co(III) complexes derived from Co(Salpr) and [Co(CN)₅]^3? reacted with 2,6-di-$\text{t}$-butyl-$\text{p}$-benzoquinone methides to give 2,6-di-$\text{t}$-butyl-$\text{p}$-benzoquinone and 2,6-di-$\text{t}$-butyl-2,5-cyclohexadienonespirooxiranes as the main products, which are considered to result from nucleophilic attack by the superoxo species on the exo double bond of the quinone methides.     

Decomposition of arilazides and p-tosylazide by thf/n-botyllithium. A new source of diazomethmne

Variously substituted arylazides, as well as $\text{p}$-tosylazide, when allowed to react at room temperature with THF previously treated with $\text{n}$-butyllithium, undergo a rapid decomposition affording the corresponding amines and fomamides, together with diazomethane. This diazo transfer (with deformylation) reaction is thought to involve the enolate of the acetaldehyde generated by the known cycloreversion of THF in the presence on $\text{n}$     

Boat-chair conformational preference of exo, exo-9-oxobicyclo[3.3.1]nonane-2,4-dicarboxylic acid

The ¹H and ¹³C nmr spectra of $\text{exo}$, $\text{exo}$-9-oxobicyclo[3.3.1]nonane-2,4-dicarboxylic acid, 3, in DMSO-d₆ or alkaline D₂O, clearly show that it exists in a $\text{boat}$-$\text{chair}$-conformation with $\text{equatorial}$ carboxyl groups, thus being the first case of $\text{boat}$-$\text{chair}$ preference of a bicyclo[3.3.1] nonan-9-one due to the presence of $\text{exo}$,$\text{exo}$-2,4- substituents.     

Facile synthesis of p-chloromethylated styrene by elimination reaction of p-(2-bromoethyl)benzylchloride using potassium hydroxide as a base under phase transfer catalysis

Phase transfer catalyzed elimination reactions of $\text{p}$-(2-bromoethyl)-benzylchloride with potassium hydroxide gave $\text{p}$-chloromethylated styrene in high yield.     

Oxygenation of p-nitrophenylhydrazones with Co(II)-schiff base complexes

$\text{p}$-Nitrophenylhydrazones, unsusceptible to autoxidation, are readily oxygenated in the presence of a five-coordinate cobalt(II)-Schiff base complex, Co(II)(MeOSalen) (Py) leading to quantitative formation of novel 1-($\text{p}$-nitrophenylazo)-1-peroxy Co(III) complexes 2, which were isolated as crystals. A plausible mechanism involving hydrogen abstraction by Co(III)(O₂^?.) from the substrate followed by formation of a substrate anion Co(III) complex intermediate is proposed.     

Synthesis of N-benzoyl-L-daunosamine from D-threonine

The synthesis of N-benzoyl-$\text{L}$-daunosamine (14) from the C₄$\text{threo}$ aldehyde (2b), prepared from $\text{D}$-threonine, through the intermediacy of the C₇ adduct (7a) is reported     

Synthesis of N-benzoyl L- and D-2,3,6-trideoxy-3-aminoxylo-hexose from non-carbohydrate precursors

The enantiomeric alcohols ($\text{2}$) and ($\text{11}$), obtained from (2$\text{R}$,3$\text{R}$) tartaric acid and, respectively, $\text{L}$-threonine, have been used to construct the C₆, enantiomeric deoxy amino sugar derivatives ($\text{7}$) and ($\text{12}$)     

Enantiocontrolled synthesis of (S)-3-substituted cycloalkanones from (s)-2-(p-tolylsulfinyl)-2-cycloalkenones and diorganomagnesium reagents.

By appropriate choice of reaction conditions, the $\text{same}$ enantiomerically pure ($\text{S}$)-(+)-2-($\text{p}$-tolylsulfinyl)cycloalkenone can be converted into $\text{either}$ an ($\text{R}$)-or an ($\text{S}$)-3-substituted cycloalkanone in good to excellent enantiomeric purity.     

[2+2] Cycloaddition of benzyne to cis,trans- and cis,cis-1,5-cyclooctadiene

The relative rates of formation of $\text{cis}$ and $\text{trans}$ [2+2]cycloadducts of benzyne to $\text{cis}$, $\text{trans}$- and $\text{cis}$, $\text{cis}$-1,5-cyclooctadiene, $\text{trans}$- and $\text{cis}$-cyclooctene are discussed and properties of the adducts (e.g., their unusual hydrogenation) are described.     

Preparation of halo-F-methanes via potassium fluoride-halogen cleavage of halo-F-methylphosphonium salts

Treatment of halo-$\text{F}$-methylphosphonium salts with potassium fluoride and halogen (I₂, Br₂, ICl, IBr) gives modest yields of halo-$\text{F}$-methanes. This method of preparation augments the classical Hunsdiecker approach to these materials.     

Diastereoselective synthesis of N-acetyl-D,L-acosamine and N-benzoyl-D,L-ristosamine

N-Acyl derivatives of $\text{D}$,$\text{L}$-acosamine and $\text{D}$,$\text{L}$-ristosamine were synthesized with high stereo selectivity utilizing intramolecular Michael addition of γ- and δ-carbomoyloxy-α,β-unsaturated esters.     

Mechanism of selective p-quinol formation in the cobalt schiff base complex-catalyzed oxygenation of 4-alkyl-2,6-di-t-butylphenols

The selective formation of $\text{p}$-quinols in the Co(Salpr)-catalyzed oxygenation of 4-alkyl-2,6-di-$\text{t}$-butylphenols in MeOH has been found to involve the rate determining reduction of peroxy-$\text{p}$-quinolato Co(III) complex formed in the initial fast step. An ionic mechanism of the reduction of the OO bond in the peroxy complex by MeOH has been discussed based on kinetic studies. The reactive species in the catalytic cycle is found to be [Co(III)(Salpr)(OH)].     

Plaunol A and B,new anti-ulcer diterpenelactones from Crotonsublyratus

Two new diterpenelactones named plaunol A ($\text{2}$) and B ($\text{3}$) exhibiting anti-Shay ulcer activity were isolated from Thai medicinal plant, $\text{Croton}$$\text{sublyratus}$. Structure of $\text{2}$ was determined by X-ray analysis of its $\text{p}$-bromobenzoate and structure of $\text{3}$ was deduced from the results of chemical correlation and the spectral data.     

Some remarkable oxidations of 2,3,5,6-tetrachloro-p-phenylenediamine,and products therefrom

The oxidation of 2,3,5,6-tetrachloro-$\text{p}$-phenylenediamine with Cl₂ or Br₂ in CCl₄ containing I₂ affords unusual quinoniminium salts displaying remarkable chemical behaviour.