Polyene natural products

Thirsk, Carl; Whiting, Andrew

doi:10.1039/b109741p

Cited by 191 publications

(147 citation statements)

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“…[5] However,i nternal 1,3-enynes, an important category of substrates, were identified asp roblematic startingm aterials in Fürstner's system. This limitation significantly restricts the stereodefined synthesis of 1,3-diene derivatives, which are important structural motifs in many natural products [6] and are widely used in cycloaddition reactions. [7] Therefore, it is necessary to find an applicable solution for the trans hydroboration of internal 1,3-enynes, and it is indeed a challenge for chemists working in this field.…”

Section: Introductionmentioning

confidence: 99%

Mechanism and Origin of the Stereoselectivity in the Palladium‐Catalyzed trans Hydroboration of Internal 1,3‐Enynes with an Azaborine‐Based Phosphine Ligand

Yang

Jiang

et al. 2017

Chemistry A European J

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An azaborine-based phosphine-Pd catalystw as introduced by the Liu group to promote trans hydroboration of the C Ct riple bond of internal 1,3-enyne substrates. Despite the excellent yield and selectivity observed experimentally,t he mechanism and the origin of this special trans selectivity remained unknown. Herein, ac omprehensive theoretical investigation was performed to clarify these issues. Accordingly,t wo main mechanisms (inner-and outersphere) were proposed and examined. Different from the conventionali nner-sphere mechanism,i nw hich the transition metal is involved in HÀBb ond cleavage, this reaction follows an outer-sphere mechanism, in which Pd does not directlyp articipate in HÀBb ond cleavage. More specifically, the favorable pathway followed aT suji-Trost type reaction, in which the HÀBb ond was weakened by the formation of a four-coordinate boron intermediate (i.e.,t he boron is attached to the terminalc arbon of the alkyne group). It then underwent ah ydride-transfer process with the assistance of as econd borane molecule, and finally reductivee limination generated the trans hydroboration product. Further analysis ascribed the origin of the special trans selectivity to the unique steric effect and electronic effect introduced by the special k 1 -P-h 2 -BC coordinationpattern.

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Section: Introductionmentioning

confidence: 99%

Mechanism and Origin of the Stereoselectivity in the Palladium‐Catalyzed trans Hydroboration of Internal 1,3‐Enynes with an Azaborine‐Based Phosphine Ligand

Yang

Jiang

et al. 2017

Chemistry A European J

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“…[1b] In recent years, several applications of alkynyl, alkenyl and dienyl boron derivatives have been developed as functionalised building blocks in the synthesis of organic and natural products. [6,7] This fact has made this topic a growing and steadily more appealing field of research.…”

Section: Introductionmentioning

confidence: 99%

“…Indeed, a number of them have found clinical utility as drugs and antibacterial and antifungal compounds. [6][7] Boryl-substituted 1,3-dienes can be prepared by classic stoichiometric routes using organometallic reagents [10,11] or by more recently applied catalytic methods, such as hydroboration of enynes, [12] cross-coupling of 1,1-diborylated alkenes with alkenyl halides, [13] Heck coupling of vinylboronate with vinylarylic iodides, [8e, 14] as well as cross-metathesis of vinylboronates with 1,3-dienes. [15] Additionally, silylboryl-substituted dienes can be synthesised by means of nickel-catalysed silaborative dimerisation of alkynes.…”

Section: Introductionmentioning

confidence: 99%

A New Catalytic Route to Boryl‐ and Borylsilyl‐Substituted Buta‐1,3‐dienes

Walkowiak

Jankowska‐Wajda

Marciniec

2008

Chemistry A European J

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Vinyl-substituted boronates in the presence of complexes containing Ru-H bonds (preferably [Ru(CO)ClH(PCy(3))(2)], Cy: cyclohexyl) react regioselectively with terminal ethynes (involving silylethynes), albeit with the exception of phenylacetylene, to produce boryl- and borylsilyl-substituted buta-1,3-dienes with a preference for E,E-diene. The reaction opens a new catalytic route for the preparation of dienylboronates, and particularly dienylsilylboronates, that are functionalised building blocks in the synthesis of organic and natural products. The mechanism of this new reaction was proved to involve an insertion of alkyne into Ru-H bonds followed by an insertion of coordinated vinyl boronate into the Ru-C= bond and beta-hydrogen transfer to the metal to eliminate boryldiene or borylsilyldiene.

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“…The possibility for easy exchange of metalloids from these compounds and the introduction of various functional groups are very attractive for chemists. Hence, olefins and alkynes substituted with silyl, boryl, germyl or stannyl moieties have found broad application in the formation of specialty and fine chemicals [1][2][3][4][5][6][7].…”

Section: Introductionmentioning

confidence: 99%