José Gustavo Ávila-Zárraga

REGIO AND STEREO SELECTIVITY ON THE α-ARYL-δ-EPOXYNITRILE ANIONIC CYCLIZATION REACTIONS: MODULATION TOWARDS A 5-ENDO OR 4-EXO PROCESS

Here we present a study focused on the regio and stereoselectivity of the anionic intramolecular cyclization reactions of several 4-(3,3-dimethyloxiran-2-yl)-2-arylbutanonitriles. The first part comprises the exploration of the reaction varying the temperature/solvent as well as the base counter-ion; switching between Li, Na and K that companies hexamethyldisilylamide anion. This is a well-known base used widely. In the second part, we provide a pair of methodologies that lead almost exclusively to pentacarbocycles through a 5-endo pathway, although is known to be a non-favored process in many cases. We found that both the metal counter-ion and the temperature have an important effect on the regioselectivity of the reaction and, independently of the pathway presented, the preferred diastereoselectivity is trans.

One-Pot Synthesis of New 6-(Alkylamine)Dibenzo[c,e][1,2]Oxaphosphinine-6-Oxides

ABSTRACT Several new 6-(alkylamine)-6H-dibenz[c,e][1,2]oxaphosphinine-6-oxides were prepared through a one-pot reaction, starting with 2-phenylphenol, phosphorus trichloride, and a Zn catalyst, to form 6-chloro-6H-dibenz[c,e][1,2]oxaphosphine. The alkylamine derivatives were subsequently prepared through a nucleophilic substitution reaction involving aliphatic amines and H2O2 oxidation under soft conditions. This method has the advantages that it is a one-pot synthesis, does not require an inert atmosphere, and involves in situ catalyst formation. GRAPHICAL ABSTRACT

Alkylation of Dimethyl 1,3-Acetonedicarboxylate

Abstract A reliable, reproducible, general, and detailed procedure for the alkylation of dimethyl-1,3-acetonedicarboxylate is described.

Reducción de nitrocompuestos utilizando el sistema Pd/H2N-NH2/Mw

1 ABSTRACT (Reduction of nitro compounds using the Pd/H2N-NH2/Mw system) The reduction of nitro compounds to obtain the corresponding amines is one of the most use - ful reactions in organic synthesis. Of the various methods for achieving such reductions, those based on the transfer of atoms using Hydrogen donors have several advantages over catalytic hydrogenation or reductions via metal/acidic medium, especially due to low complexity in- volved in experimental development, and in addition to low toxicity of the products. In addi- tion to this and taking the precepts of green chemistry, it is preferred the production of new compounds preventing the generation of hazardous wastes and minimizing the impact on health and the environment. Thus, the goal of this paper is to provide an alternative process for the reduction of nitro compounds by using: a) the Pd/H2N-NH2 system in very easy condi- tions, and b) alternative heating such as microwave energy, with good yields and very short reaction periods.

A Total Synthesis of the Antibiotic DB-2073

Abstract A convergent aromatic annulation strategy based on the Michael addition of the dimethyl-1,3-acetonedicarboxylate 1 anion to 2-hexynal 2, followed by a regiocontrolled Dieckmann-type cyclization, has been applied to a total synthesis of the antibiotic, DB-2073 I. This tandem annulation reaction generates the fully substituted aromatic intermediate 3, which was transformed by a five-step sequence to I. In recent years we have developed a total and a formal synthesis of mycophenolic acid [Covarrubias-Zúñiga, A.; González-Lucas, A. Tetrahedron Lett. 1998, 39, 2881; Covarrubias-Zúñiga, A.; Díaz-Domínguez, J.; Olguín-Uribe, J.S. Synthetic Communications 2001, 31, 1373.] using as key step tandem reactions based on Michael addition and intramolecular Dieckmann-cyclization; In this article we utilize this synthetic approach for the total synthesis of the resorcinol DB-2073 I. This tetrasubstituted resorcinol was isolated and purified from pseudomonas B-9004, showing antibacterial and antifungal activities [Kanda, N.; Ishizaki, N.I.; Oshima, M.; Handa, A.; Kitahara, T.J. Antibiotics 1975, 28, 935.]. The molecular formula of DB-2073 was established by spectroscopic methods [Kitahara, T.; Kanda, N. J. Antibiotics 1975, 28, 943.], as 2-hexyl-5-propyl-resorcinol I.