Diego Armesto

8-Functionalization of alkyl-substituted-3,8-dimethyl BODIPYs by Knoevenagel condensation.

New 8-alkenylBODIPYs have been synthesized by Knoevenagel condensation between a series of alkyl-substituted-3,8-dimethylBODIPYs and aromatic or aliphatic aldehydes. This is in clear contrast with literature precedents, which indicate that this reaction occurs exclusively on the methyl group at C-3. The change in hybridization of the carbon at the 8-position (from sp(3) to sp(2)) determines the fluorescence emission of the BODIPY, while the presence of electron-donating or -withdrawing groups leads to intramolecular charge transfer processes.

A novel aza-di-Π-methane rearrangement the photoreaction of 4,4-dimethyl-1,6,6-triphenyl-2-aza-hexa-2,5-diene

Abstract The synthesis and the novel photochemical aza-di-π-methane reaction of 4,4-dimethyl-1,6,6-triphenyl-2-aza-hexa-2,5-diene are described.

A new photochemical synthesis of cyclopropanecarboxylic acids present in pyrethroids by the aza-di-π-methane rearrangement

Abstract A novel synthetic route to chrysanthemic acid, 2-cyclopentylidenmethyl-3,3-dimethylcyclopropanecarboxylic acid, fluorenespiro-2,2-dimethylcyclopropanecarboxylic acid and indenespiro-2,2-dimethylcyclopropanecarboxylic acid, all of them present in pyrethroids of known insecticidal activity, is described. The key step in the synthesis is the aza-di-n-rnethane rearrangement of some 1-aza-1,4,6-trienes and some 1-aza-1,4-dienes, using triplet sensitization.

SmI2-mediated 3-exo-trig cyclization of β,γ-unsaturated carbonyl compounds: diastereoselective synthesis of cyclopropanols.

SmI(2)-mediated 3-exo-trig cyclizations of β,γ-unsaturated carbonyl compounds to generate cyclopropanols are not generally observed processes. The reported examples are limited to β,γ-unsaturated carbonyl compounds that possess ester groups conjugated with the alkene unit. The results of the current study show that this cyclization also occurs when other substitution patterns are present on the alkene moiety, affording (E)-cyclopropanols in good to excellent yields and in most cases with high degrees of diastereoselectivity.

The aza-di-π-methane rearrangement of β,γ-unsaturated oximes

Although previous studies have shown that acyclic β,γ-unsaturated oximes and oxime ethers do not undergo the aza-di-π-methane (ADPM) rearrangement, the 2-methyl-4,4-diphenyl-2-vinylbut-3-enal oxime 5a, its methyl ether 5b and the 2,2,4,4-tetraphenylbut-3-enal oxime 14 give the corresponding cyclopropyl derivatives 8a, 8b and 15 by the ADPM path, in a reaction that is controlled by the stability of the intermediate 1,3-biradical.

Studies on the scope of the aza-di-π-methane rearrangement of β,γ-unsaturated imines

The syntheses of imines of 2,2,4,4-tetraphenylbut-3-enal, 3,3-dimethyl-5,5-diphenylpent-4-en-2-one, and 2,2-dimethyl-1,4,4-triphenylbut-3-en-1-one are described. The results of the irradiation of these and of 2,2-dimethyl-4,4-diphenylbut-3-enonitrile and 2,2-dimethyl-4,4-diphenylbut-3-enal oxime are discussed. The N-isopropyl imine of 2,2,4,4-tetraphenylbut-3-enal and the N-phenyl and benzyl imines of 3,3-dimethyl-5,5-diphenylpent-4-en-2-one undergo the 1-aza-di-π-methane rearrangement.

A novel photochemical synthesis of 5,6-dihydro-4H-1,2-oxazines by DCA-sensitized irradiation of γδ-unsaturated oximes

On DCA-sensitized irradiation 6,6-diphenylhex-5-en-2-one oxime 5a, 5,5-diphenylpent-4-enal oxime 5b and 2,2-dimethyl-5-phenylpent-4-enal oxime 5c undergo a novel photochemical cyclization yielding 3-methyl-6-diphenylmethyl-5,6-dihydro-4H-1,2-oxazine 9a, 6-diphenylmethyl-5,6-dihydro-4H-1,2-oxazine 9b and 6-benzyl-4,4-dimethyl-5,6-dihydro-4H-1,2-oxazine 9c, respectively.

The Aza-di-π-methane rearrangement of O-acetyl 2,2-dimethyl-4,4-diphenylbut-3-enal oxime

The photochemical reaction of O-acetyl 2,2-dimethyl-4,4-diphenylbut-3-enal oxime is described: the reaction yields two cyclopropane derivatives, O-acetyl 3,3-dimethyl-2,2-diphenylcyclopropane carboxaldehyde oxime as the primary photoproduct, formed by an aza-di-π-methane reaction previously unobserved in such compounds, and 1-cyano-3,3-dimethyl-2,2-diphenylcyclopropane formed by thermal elimination of acetic acid from the primary product.

Substitution effects on the aza-di-π-methane rearrangement of imines

The u.v. irradiation of several 1-aryl derivatives of 3,3-dimethyl-5,5-diphenyl-1-azapenta-1,4-diene has been carried out. All of them undergo the aza-di-π-methane rearrangement and yield a cyclopropylimine. The influence of substituents on the 1-aryl group has given support for the proposal that imines with a low ionization potential are less efficient at undergoing the aza-di-π-methane process than are imines with a higher ionization potential. This was demonstrated in a quantitative fashion. The involvement of an electron-transfer process in the reaction is discussed.

A novel photochemical 1,2-acyl migration in an enol ester. The synthesis of 3-oxazoline derivatives.

Abstract Irradiation of 3-Aryl-4-benzoyloxy-1,1,4-triphenyl-2-aza-buta-1,3-dienes gives 3-oxazoline derivatives in high yield by a novel 1,2-acyl migration, in clear contrast with the normal behaviour of other enol esters.