Rapid Microwave-Induced Palladium-Catalyzed Asymmetric Allylic Alkylation

Bremberg, Ulf; Larhed, Mats; Moberg, Christina; Hallberg, Anders

doi:10.1021/jo981896h

Cited by 58 publications

(20 citation statements)

References 29 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…p-Rich and p-deficient aromatics,w here starting materialsa nd productsa re both potentially viablel igands to transition metals, [54,55,56] react smoothly affording 9h-j despite the presence of Lewis basic atoms ( Table 2, entries 10-12).…”

Section: Resultsmentioning

confidence: 99%

Efficient and Flexible Synthesis of Highly Functionalised 4‐Aminooxazoles by a Gold‐Catalysed Intermolecular Formal [3+2] Dipolar Cycloaddition

2016

View full text Add to dashboard Cite

Oxazolesa re important motifs within bioactive and functional materials.C omplex, fully substituteda nd functionalised 4-aminooxazoles are accessed by an efficienti ntermolecular reactionb etween an ynamide and an N-acylpyridinium N-aminide in the presence of ag old catalyst. Thef ormal [3+ +2] dipolar cycloaddition employs an ucleophilic nitrenoid approach to access the 1,3-N,O-dipole character in ac ontrollable fashion.T he selectivity for ac ycloaddition pathwayp rovides as tark contrast against the indiscriminate reactivity of electrophilic acyl nitrenes.P rotocolsf or the formation of acylfunctionalised aminides are reported from accessible precursors including carboxylic estersa nd acids.T he function of these aminides in the oxazole-forming reaction has been exploreda nd it is shown that substantial elaboration is accommodated despite proximity to the reactivec entre.A saresult functional oxazole-based motifs,s uch as chiral oxazoles with biologically pertinent substitution patterns,a re readily accessible.T he use of ynamide types that are unexplored or little used in gold catalysis has been evaluated. Unusual all-heteroatom substitution patterns around the oxazole are shown to be accessible using thio-ynamides.T he studys hows that ac lose stoichiometry of reactantsi ss uitable alongsider elatively low loadings of the bench-stable precatalysts in practicallys traightforward multi-mmol scale reactions.T he efficiency and flexibility of this regioselective intermolecular preparation is demonstrated in the ready synthesis of oxazoles with substantial structural and functional group variation.

show abstract

Section: Resultsmentioning

confidence: 99%

Efficient and Flexible Synthesis of Highly Functionalised 4‐Aminooxazoles by a Gold‐Catalysed Intermolecular Formal [3+2] Dipolar Cycloaddition

2016

View full text Add to dashboard Cite

show abstract

“…Since then, many metal-catalyzed reactions have been performed within minutes by microwave heating in pressurized systems, sometimes with high regio-and enantioselectivity [56,57].…”

Section: Metal-catalyzed Processesmentioning

confidence: 99%

Microwave‐Assisted Organic Chemistry in Pressurized Reactors

Strauss

2002

Microwaves in Organic Synthesis

View full text Add to dashboard Cite

The highest priorities for the chemical industry now are process and product safety and the environment [1±5]. New technologies and methods for ªgreenº and sustainable chemistry are subjects of intense activity [6]. In that regard, the potential of microwave heating for organic synthesis attracted interest soon after the first reports [7, 8] appeared in 1986. Early reactions were performed with domestic microwave ovens and relatively primitive containers. Rate enhancement of up to three orders of magnitude was observed, but the time savings were offset by hazards such as deformation of the vessels and explosions.Thus, the major challenge confronting the early microwave chemists was to retain or enhance the benefits of the technology while concurrently avoiding the risks. Several groups concluded that microwave heating was incompatible with organic solvents and investigated solvent-free conditions including ªdryº media, usually with open vessels in domestic microwave ovens [9±12]. That area expanded rapidly, aided by the ready availability of inexpensive microwave equipment and encouraged by a diverse range of reactions awaiting exploration.Synthetic chemists desire well defined reaction conditions. Process chemists demand them. Nonuniform heating and difficulties with mixing and temperature measurement are technical constraints that initially limited the scale of microwave chemistry with ªdryº media and have not yet been overcome. Poor reproducibility also has been reported, probably resulting from differences in performance and operation of individual domestic microwave ovens [13±15]. Consequently, most, if not all, of the disclosed applications of ªdryº media are laboratory-scale preparations. However, as discussed in other chapters, this does not prevent their being interesting and useful.An alternative approach, developed by Bose [16±19] and termed ªmicrowave-induced organic reaction enhancementº (MORE) chemistry, employed polar, high-boiling solvents with open vessels in unmodified domestic microwave ovens. The solvents had dielectric properties suitable for efficient coupling of microwave energy and rapid heating to temperatures that although high, were typically some 20±30 8C 35Microwaves in Organic Synthesis. Edited by Andr Loupy

show abstract

“…Dihydrooxazoles possessing several coordination centers are considered to act as bi-and tridentate ligands [1,36,[42][43][44][45][46][47]. Development of procedures for the synthesis of dihydrooxazoles is also important taking into account their wide application as medicines and building blocks for the synthesis of medical agents [48].…”

Section: Introductionmentioning

confidence: 99%