Synthesis of 3,4,5-Trisubstituted Isoxazoles via Sequential [3 + 2] Cycloaddition/Silicon-Based Cross-Coupling Reactions

Denmark, Scott E.; Kallemeyn, Jeffrey M.

doi:10.1021/jo047755z

Cited by 88 publications

(57 citation statements)

References 17 publications

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“…Palladium catalyzed cross-couplings of an alkenyldimethylbenzylsilane with iodobenzene [274], of alkenyl and aryl(2-hydroxymethyl)dimethylsilanes with aryl and alkenyl iodides (Eq. (12)) [275], of (Z)-3-trimethylsilyl-2-alkenoates [276] and of 1,4-bissilyl-1,3-butadienes with aryl iodides [277] and this reaction was utilized in a synthesis of RK-397 [278], of ␣-silyl nitriles with aryl bromides [121], of dimethyl(4-isoxazolyl)silanes with aryl iodides [279], of carbamoylsilanes with imidoyl chlorides [280] and benzyl bromides and chlorides [281], of (E)-N-(2-silylethenyl)carbazole with iodobenzene [282], of trimethyl-2-pyridylsilanes and aryl halides [283], and of dimethylfluorosilylalkenes with aryl iodides [284]. A palladium-catalyzed couplings of 5-bromotropolone and arylsiloxanes was used in an approach to colchicine [285].…”

Section: Carbon-carbon Bond-forming Reactions Via Transmetallationmentioning

confidence: 99%

Transition metals in organic synthesis: Highlights for the year 2005

Söderberg

2008

Coordination Chemistry Reviews

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Section: Carbon-carbon Bond-forming Reactions Via Transmetallationmentioning

confidence: 99%

Transition metals in organic synthesis: Highlights for the year 2005

Söderberg

2008

Coordination Chemistry Reviews

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“…47 The nitrile oxides can be generated under two different conditions, both sufficiently mild to allow the use of an alkynylsilyl methyl ether as the 2π-component. The [3+2] cycloadditions proceed in modest regioselectivity (ca.…”

Section: Silanolsmentioning

confidence: 99%

Why You Really Should Consider Using Palladium-Catalyzed Cross-Coupling of Silanols and Silanolates

Denmark

Ambrosi

2015

Org. Process Res. Dev.

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155

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The transition metal-catalyzed cross-coupling of organometallic nucleophiles derived from tin, boron, and zinc with organic electrophiles enjoys a preeminent status among modern synthetic methods for the formation of carbon-carbon bonds. In recent years, organosilanes have emerged as viable alternatives to the conventional reagents, with the added benefits of low cost, low toxicity and high chemical stability. However, silicon-based cross-coupling reactions often require heating in the presence of a fluoride source, which has significantly hampered their widespread acceptance. To address the “fluoride problem”, a new paradigm for palladium-catalyzed, silicon-based cross-coupling reactions has been developed that employs a heretofore underutilized class of silicon reagents, the organosilanols. The use of organosilanols, either in the presence of Brønsted bases or as their silanolate salts, represents an operationally simple and mild alternative to the fluoride-based activation method. Organosilanols are readily available by many well-established methods for introducing carbon-silicon bonds onto alkenes, alkynes, arenes and heteroarenes. Moreover, several different protocols for the generation of alkali metal salts of, vinyl-, alkenyl-, alkynyl-, aryl-, and heteroarylsilanolates have been developed and the advantages of each of these methods have been demonstrated for a number of different coupling classes. This review will describe the development and implementation of cross-coupling reactions of organosilanols and their conjugate bases, silanolates, with a wide variety of substrate classes. In addition, application of these transformations in the total synthesis of complex natural products will also be highlighted. Finally, the unique advantages of organosilicon coupling strategies vis a vis organoboron reagents are discussed.

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“…Therefore, many synthetic approaches have been reported for the formation of the isoxazole core, including reactions of hydroxylamine with 1,3-dicarbonyl compounds, a,b-unsaturated carbonyl compounds, and a, b-unsaturated nitriles [8]. In addition, [3 + 2] cycloadditions of alkynes and nitrile oxides represent an elegant and concise access to this class of compounds [9]. Although, these strategies are highly convergent, in many cases either strong bases or strong mineral acids are required, or prolonged heating at elevated temperatures is necessary.…”

Section: Introductionmentioning

confidence: 99%