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Gilheany, Declan G.
Preferred name
Gilheany, Declan G.
Official Name
Gilheany, Declan G.
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Now showing 1 - 10 of 12
- PublicationStructure-activity relationship of a novel family of cysteinyl leukotriene receptor antagonist quinoline compounds with anti-angiogenic activity(British Pharmacological Society, 2017-04-01)
; ; ; ; ; ; ; ; ; ; ; Introduction: Previously, we identified quininib (2-[(E)-2-(quinolin-2-yl)vinyl]phenol), a cysteinyl leukotriene receptor antagonist with anti-angiogenic and anti-permeable activity (1,2). Here, we report a structure activity relationship study to more comprehensively characterise features which confer anti-angiogenic activity.22 - PublicationThe modern interpretation of the Wittig reaction mechanismThe mechanism of the Wittig reaction has long been a contentious issue in organic chemistry. Even now, more than 50 years after its announcement, its presentation in many modern undergraduate textbooks is either overly simplified or entirely inaccurate. In this review, we gather together the huge body of evidence that has been amassed to show that the Li salt-free Wittig reactions of non-stabilised, semi-stabilised and stabilised ylides all occur under kinetic control by a common mechanism in which oxaphosphetane (OPA) is the first-formed and only intermediate. The numerous recent significant additions to the subject – including computational studies and experimental material pertinent to both steps of the reaction (OPA formation and its decomposition) are discussed in detail, and the currently accepted explanations for the source of the stereoselectivity in Wittig reactions are given. We also present the other mechanistic proposals that have been made during the history of the Wittig reaction, and show how they are unable to account for all of the experimental evidence that is now available. Details of certain experimental facts to do with Wittig reactions in the presence of Li cation are also included, although the precise mechanistic details of such reactions are yet to be established conclusively. We make the case that a clear distinction should henceforth be made between the unknown “Li-present” and the now well-established “Li salt-free” Wittig mechanisms.
2642Scopus© Citations 236 - PublicationA convenient and mild chromatography-free method for the purification of the products of Wittig and Appel reactions(RSC Publishing, 2012-03)
; ; ; A mild method for the facile removal of phosphine oxide from the crude products of Wittig and Appel reactions is described. Work-up with oxalyl chloride to generate insol. chlorophosphonium salt (CPS) yields phosphorus-free products for a wide variety of these reactions. The CPS product can be further converted into phosphine.1119Scopus© Citations 69 - PublicationDirect evidence of a multicentre halogen bond: unexpected contraction of the P–XXX–P fragment in triphenylphosphine dihalidesTriphenylhalophosphonium halides, Ph3PX2, form crystals comprising bridged linear cations [Ph3P-X-X-X-PPh3]+ where the X3 bridge is shortened from 6.56 Å in Cl-Cl-Cl to 6.37 Å in the Br-Br-Br system. It is proposed that this structure is stabilized by five-center/six-electron (5c-6e) hypervalent interactions.
379Scopus© Citations 26 - PublicationAn easy and short preparation of pentachloroacetone by selective dechlorination of hexachloroacetone under Appel conditionsWe report a very convenient laboratory preparation of pentachloroacetone (PCA) by selective dechlorination of hexachloroacetone (HCA) via reaction with triphenylphosphine in the presence of methanol or aromatic alcohols.
453Scopus© Citations 5 - PublicationUnequivocal experimental evidence for a unified lithium salt-free Wittig reaction mechanism for all phosphonium ylide types: reactions with β-heteroatom-substituted aldehydes are consistently selective for cis-oxaphosphetane-derived productsThe true course of the lithium salt-free Wittig reaction has long been a contentious issue in organic chemistry. Herein we report an experimental effect that is common to the Wittig reactions of all of the three major phosphonium ylide classes (non-stabilized, semi-stabilized, and stabilized): there is consistently increased selectivity for cis-oxaphosphetane and its derived products (Z-alkene and erythro-B-hydroxyphosphonium salt) in reactions involving aldehydes bearing heteroatom substituents in the B-position. The effect operates with both benzaldehydes and aliphatic aldehydes and is shown not to operate in the absence of the heteroatom substituent on the aldehyde. The discovery of an effect that is common to reactions of all ylide types strongly argues for the operation of a common mechanism in all Li salt-free Wittig reactions. In addition, the results are shown to be most easily explained by the [2+2] cycloaddition mechanism proposed by Vedejs and co-workers as supplemented by Aggarwal, Harvey, and co-workers, thus providing strong confirmatory evidence in support of that mechanism. Notably, a cooperative effect of ortho-substituents in the case of semi-stabilized ylides is confirmed and is accommodated by the cycloaddition mechanism. The effect is also shown to operate in reactions of triphenylphosphine-derived ylides and has previously been observed for reactions under aqueous conditions, thus for the first time providing evidence that kinetic control is in operation in both of these cases.
923Scopus© Citations 61 - PublicationAnomalous Z-isomer content in Wittig reaction products from keto-stabilised ylides with ortho-heteroatom substituted benzaldehydesWittig reaction products of keto-stabilised ylides with ortho-substituted benzaldehydes are found to show significantly higher than expected Z-alkene content (up to 50%) compared to analogous reactions of the same ylides with benzaldehyde itself. A cooperative effect is seen whereby the unusual Z-content is further augmented if the ylide bears greater steric bulk in the α′-position. These results are consistent with our previous observations on reactions of all ylide types with aldehydes bearing a β-heteroatom. Significantly, the cooperative effect, previously seen only with semi-stabilised ylides, has now been extended to stabilised ylides. Both the anomalous increase in Z-content and the cooperative effect can be rationalised within the [2+2] cycloaddition mechanism of the Wittig reaction.
453Scopus© Citations 14 - PublicationSynthesis of 2,3-Dihydro-1-phenylbenzo[b]phosphole (1-Phenylphosphindane) and Its Use as a Mechanistic Test in the Asymmetric Appel Reaction: Decisive Evidence against Involvement of Pseudorotation in the Stereoselecting Step(American Chemical Society, 2013-09-30)
; ; ; ; Racemic 2,3-dihydro-1-phenylbenzo[b]phosphole was obtained by reduction of 1-phenylbenzo[b]phosphole-1-oxide, itself derived by ring-closing metathesis of phenylstyrylvinylphosphine oxide. The title compound was then reoxidized under asymmetric Appel conditions. Comparison of the sense and degree of the stereoselectivity to those obtained with an open-chain analogue indicated that the ring system does not affect the selectivity of the process. This in turn strongly suggests that the stereoselection is not related to pseudorotamer preferences in putative phosphorane intermediates.360Scopus© Citations 26 - PublicationA U-Turn in the Asymmetric Appel Reaction: Stereospecific Reduction of Diastereomerically Enriched Alkoxyphosphonium Salts Allows the Asymmetric Synthesis of P-Stereogenic Phosphanes and Phosphane Boranes(Wiley, 2012-04-05)
; ; ; An efficient one-pot synthesis has been developed of enantioenriched P-stereogenic phosphanes and phosphane boranes from the corresponding racemic phosphanes in excellent yield under asymmetric Appel conditions. The chiral auxiliary (menthol) can also be recovered unchanged. The simple and efficient protocol significantly expands the scope of our asymmetric Appel process. The crucial step in the preparation involves stereospecific reduction of intermediate diastereomeric alkoxyphosphonium salts, which are obtained in the reaction of phosphane, hexachloroacetone, and menthol. Thereby, reaction with LiAlH4 or NaBH4 gives the corresponding phosphanes or phosphane boranes, respectively.422Scopus© Citations 29 - PublicationCleavage of P=O in the Presence of P-N: Aminophosphine Oxide Reduction with In Situ Boronation of the PIII Product(Wiley-VCH, 2013-10-11)
; ; ; In contrast to tertiary phosphine oxides, the deoxygenation of aminophosphine oxides is effectively impossible due to the need to break the immensely strong and inert PO bond in the presence of a relatively weak and more reactive PN bond. This long-standing problem in organophosphorus synthesis is solved by use of oxalyl chloride, which chemoselectively cleaves the PO bond forming a chlorophosphonium salt, leaving the PN bond(s) intact. Subsequent reduction of the chlorophosphonium salt with sodium borohydride forms the PIII aminophosphine borane adduct. This simple one-pot procedure was applied with good yields for a wide range of PN-containing phosphoryl compounds. The borane product can be easily deprotected to produce the free PIII aminophosphine. Along with no observed PN bond cleavage, the use of sodium borohydride also permits the presence of ester functional groups in the substrate. The availability of this methodology opens up previously unavailable synthetic options in organophosphorus chemistry, two of which are exemplified.545Scopus© Citations 25