RESUMEN

A molecular mechanics force field has been developed which accurately reproduces experimental solid state structures and conformer interconversion barriers for a series of sterically congested diaryl and triaryl phosphines and some of their chalcogenide and Cr(CO)5 derivatives.

RESUMEN

The reaction between the heteroaromatic N-oxides 1a, 1b and 1c with dimethyl acetylenedicarboxylate or methyl propiolate furnishes 1,3-benzodiazepines, the products of ring transformations of primarily formed cycloadducts. The structures of 8a and 10a have been confirmed by X-ray crystallographic analysis. The aldonitrone 1c also reacts with N-methylmaleimide and with phenyl vinyl sulfone to furnish the first examples of primary cycloaddition products from quinazoline 3-oxides.

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RESUMEN

The pharmaceutical compound bicifadine hydrochloride, which has been found to crystallize in two polymorphic forms, has been characterized by thermal analysis, X-ray powder diffraction (XRPD), infrared (IR) spectroscopy, and near-infrared (NIR) spectroscopy. A series of 22 sample mixtures of polymorph 1 and polymorph 2 were prepared and calibration models for the quantitation of these binary mixtures have been developed for each of the XRPD, attenuated total reflectance (ATR)-IR, and ATR-NIR analytical techniques. The quantitative results were obtained using a partial least squares (PLS) algorithm, which predicted the concentration of polymorph 1 from the XRPD spectra with a root mean standard error of prediction (RMSEP) of 4.4%, from the IR spectra with a RMSEP of 3.8%, and from the NIR spectra with a RMSEP of 1.4%. The studies indicate that when analyses are carried out on equivalent sets of spectra, NIR spectroscopy offers significant advantages in quantitative accuracy as a tool for the determination of polymorphs in the solid state and is also more convenient to use than both the ATR-IR and XRPD methods. Density functional theory (DFT) B3LYP calculations and IR spectral simulation have been used to determine the nature of the vibrational modes that are the most sensitive in the analysis.

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RESUMEN

Preparation of a series of terminally and internally substituted delta-alkenyl and delta-alkynyl esters 6, 7 and 9, potential precursors to oxazin-2-one nitrones, has been attempted. Condensation between pyruvic or benzoylformic acid and the appropriate alcohol proceeded smoothly in some cases whilst allylic transposition was a major feature in other cases--most especially during reactions with alpha-vinylbenzyl alcohol. Oximation of pyruvic acid derivatives furnished E-oxime isomers whilst benzoylformic acid derivatives afforded mixed geometrical isomers. The E-oxime of 4a1 carrying an internal Me group undergoes facile thermal cyclisation affording nitrones 1c and 1d in good yield. Oximes E-5a,b with a terminal methyl substituent on the alkene moiety furnish nitrone only under the influence of an external electrophile [PhSeBr/AgBF4]. A terminal Ph substituent on 5c,d prohibits formation of the cyclic dipole irrespective of reaction conditions, and whilst 5d reacts to afford a bicyclic isoxazolofuranone 13 by an IOOC reaction (intramolecular oxime olefin cyclisation) 5c remains thermally inert. Finally delta-alkynyl oximes 9c,d also failed to cyclise. The regio- and stereochemical characteristics of the cycloadditions between the new dipoles and electron poor olefinic dipolarophiles have been investigated. The conditions needed for reaction were rather forcing since the dipoles are somewhat stabilised by the adjacent alkoxycarbonyl group. All reactions proceeded regiospecifically to give adducts with 5-substituted isoxazolidine rings whilst diastereoselectivity varied with the choice of dipolarophile and the steric demands of the nitrone substituents. The phenylselenyl dipole 10a could not be trapped by any dipolarophiles bar dimethyl acetylenedicarboxylate.

RESUMEN

alpha-Keto amides 10a,b, formed from reaction of pyruvic or benzoylformic acid with allyl amine are found to present as single rotameric forms whilst their tertiary amido analogues 10c, d present as two rotamers in solution at rt. The hydroxyimino derivatives 8 share the conformational characteristics of their parents. The geometrical make-up of the new alpha-amidooximes is seen to depend on the structure of the starting acid and on the degree of substitution of the amido group. The oxime 8a derived from pyruvic acid and allyl amine is formed solely as the (E)-isomer whilst its tertiary amido analogue 8c is formed as both (E)- and (Z)-isomers. Oximes derived from benzoylformic acid have the opposite selectivity with both geometrical isomers forming from the secondary amide 8b and only the (Z)-isomer from the tertiary amide 8d. With the exception of 8b all oximes were configurationally stable with (Z)-isomers reacting to form isoxazolopyrrolidinones 11--compounds with a relatively rare bicyclic nucleus and (E)-isomers cyclising to piperazin-5-one nitrones 1--ketopiperazine N-oxides have to date only appeared once in the literature. New nitrones were trapped with phenyl vinyl sulfone, dimethyl acetylenedicarboxylate and methyl propiolate yielding isoxazolidine and isoxazoline fused piperazinones 13, 15, 21 and 22. Cycloadducts from dimethyl acetylenedicarboxylate and 8a, b are thermally labile and their rearrangement provides a novel route to pyrrolopiperazinones 16. The structure of a representative isoxazolopyrrolidinone, 11c, and a 2,3-dihydroisoxazoline fused piperazinone, 21b, are unambiguously solved following x-ray structural analysis.