A 2-pyrone cycloaddition route to functionalised aromatic boronic esters

Delaney, Patrick M.; Browne, Duncan L.; Adams, Harry; Plant, Andrew; Harrity, Joseph P. A.

doi:10.1016/j.tet.2007.08.118

Cited by 44 publications

(15 citation statements)

References 38 publications

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“…Propiolic acid is commercially available in both 13 C and 14 C labelled forms, providing a comparatively simple access into specifically substituted point‐labelled arenes. The process tolerates a variety of substituents on the acetylene including aryl,129 boronate,130 hydroxyalkyl,131 phosphonium,132 silyloxy133 and trihalomethyl groups 134. Dienes used include Danishefsky's diene,126 pyranones including those bearing acylamino135 and arylthio substituents,136 diene‐substituted α‐amino acids137 and carbohydrate‐derived homochiral dienes 138.…”

Section: Cycloadditionmentioning

confidence: 99%

Synthetic approaches to regiospecifically mono‐ and dilabelled arenes

Gregson

Herbert

Row

2011

Labelled Comp Radiopharmac

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A variety of methods for the preparation of selectively mono-, di-or tri-labelled arenes are reviewed. The review concentrates on those for which the application to labelled synthesis has been demonstrated. Further methods, the application of which to labelled synthesis appears viable but which have not been reduced to practise, are included also. The available methods provide a range of substitution patterns.

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Section: Cycloadditionmentioning

confidence: 99%

Synthetic approaches to regiospecifically mono‐ and dilabelled arenes

Gregson

Herbert

Row

2011

Labelled Comp Radiopharmac

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“…100.46 (12) The X-ray crystal structure showed that 2 exhibits typical C-C and C-B bond lengths for an alkynylboronate [24]. Moreover, the C-P bond length is marginally longer than those found in related alkynylphophonium salts, where conjugation is not possible [25].…”

Section: Resultsmentioning

confidence: 98%

Synthesis, Characterisation and Reactions of Phosphine-Substituted Alkynylboronates and Alkynyltrifluoroborate Salts

et al. 2014

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Abstract:The synthesis and structural characterisation of phosphine-substituted alkynylboronates is reported. A P(III)-centred alkynylboronate (2) was prepared that showed little evidence for the conjugation of the P-lone pair to the boron via the alkyne π-system, as judged by X-ray crystallography studies of 2 and a related P(V) compound, 3. In addition, corresponding alkynyltrifluoroborate salts were prepared that showed improved stability by comparison to their boronic ester counterparts. These salts undergo Pd-catalysed cross-coupling reactions with aryl halides.

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“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] Moreover, the cycloaddition products can be used in subsequent reactions to obtain complex structures. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] Moreover, the cycloaddition products can be used in subsequent reactions to obtain complex structures.…”

Section: Introductionmentioning

confidence: 99%

Competing mechanisms for the reaction of dichloropropynylborane with 2-tert-butylbutadiene. Diels–Alder reaction versus alkynylboration

Vallejos

Pellegrinet

2015

RSC Adv.

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Density functional theory and the quantum theory of atoms in molecules approach were used to study two competing process: the Diels-Alder reaction (DA) and the 1,4-alkynylboration (AB) between dichloropropynylborane (1) and 2-tertbutylbutadiene (2) in dichloromethane. We analyzed several reaction pathways related with such reactions for both orientations (meta and para). The stepwise mechanisms for the two competitive reactions share the first step that leads to an intermediate zwitterionic structure. The second step is more favorable for the reaction occurring via TSC-m that leads to the meta enyne product 5, which is the kinetic product. The formation of the meta DA product cannot be explained through a direct cycloaddition, due to the higher activation free energy of the associated transition structure (TSB-m). An alternative transition structure with [4 + 3] character (TSD-m) that connects the meta enyne 5 with the meta cycloadduct 3 was found. We propose that at longer reaction times, 5 rearranges to the thermodynamic product 3 via TSD-m passing by a six-membered ring structure and a seven-membered ring structure. The topological analysis of the charge density along the selected reaction coordinates provided some understanding on the intriguing competitive reactions. ConclusionsThe reaction of dichloropropynylborane (1) with 2-tertbutylbutadiene (2) has been studied using density functional theory and the QTAIM approach in DCM in order to rationalize the mechanisms associated with the competing DA and AB reactions, and the origin of the experimental regioselectivity.

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A 2-pyrone cycloaddition route to functionalised aromatic boronic esters

Cited by 44 publications

References 38 publications

Synthetic approaches to regiospecifically mono‐ and dilabelled arenes

Synthetic approaches to regiospecifically mono‐ and dilabelled arenes

Synthesis, Characterisation and Reactions of Phosphine-Substituted Alkynylboronates and Alkynyltrifluoroborate Salts

Competing mechanisms for the reaction of dichloropropynylborane with 2-tert-butylbutadiene. Diels–Alder reaction versus alkynylboration

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