Maricruz Sánchez-Zavala

MICROWAVE-ASSISTED SYNTHESIS OF 3,1-BENZOXAZIN-2-ONES FROM 3-HYDROXYOXINDOLES

A general protocol for the synthesis of 3,l-benzoxazin-2-ones 18 from 3-liydroxyoxindoles 16 in a two steps sequence through phenylsuccinates or phenylpropionates 17 is described. Best reaction conditions for ring opening of 16 to succinates or propionates 17 were achieved using alcohol/silica gel, while cyclization of 17 to benzoxazinones 18 was easily done with HCl/alcohol. It was also found that 17 and 18 can be transesterified using HCl/alcohol. Most transformations were carried out by traditional heating and by microwave (MW) irradiation to accelerate reaction rates.

Regioselective Synthesis of 3-Indolyl(alkoxy)acetates

The regioselective synthesis of N-carbomethoxy-2-alkoxyindolenines and a-alkoxyindoles is reported. Brornination of indole 5 with NBSlAIBNlCC14 gave a-bromoindole 6 which after treatment with ROHI3A molecular Sieves afforded (Z-) and (E)-2-alkoxyindolenines 8a-d as the main products, together with minor amounts of a-alkosyindoles 9a-d. The reversed regioselectivity was achieved in the absence of molecular Sieves to give a-alkoxyindoles 9a-d as the main products, while no traces of Z- or E-8a-d were detected.

Complete 1H NMR assignment of 3-formylindole derivatives.

3-Formylindoles including indolylglyoxylate esters and indolylglyoxylamides are widely found in nature as alkaloids, and are important building blocks or synthetic intermediates for drug discovery, and for the synthesis of natural products. A careful inspection of the H NMR data of these molecules reveals that multiplicities for H4 and H7 are reported as broad doublets, as doublet of doublets-like, as a combination of doublet of doublets and multiplets, or simply as doublets. In the case of H5 and H6, they are reported as triplet of doublets, as triplets, or as doublet of triplets despite the fact that in most cases, their chemical shifts are claimed to be unambiguously assigned. In addition, incorrect coupling constant values for the incorrect multiplicities for H4–H7 are also reported. A prudent signal description of the H4–H7 system is rarely given asmultiples without reporting coupling constant values. Consequently, we describe herein complete and accurate chemical shift and coupling constant assignments for H4–H7 in representative series, using compounds 1–10, which followed after spectral analysis using the PERCH software and selective proton irradiations.