ABSTRACT
The metalation of 4,4-dimethyloxazoline using TMPZnCl·LiCl provides a stable 2-zincated oxazolinyl reagent which readily undergoes palladium-catalyzed Negishi cross-couplings allowing a new access to 2-aryloxazolines. Cu-mediated acylation and allylation reactions also proceed in good yields.
Subject(s)
Organometallic Compounds/chemistry , Oxazoles/chemistry , Piperidines/chemistry , Zinc/chemistry , CatalysisABSTRACT
A Lewis acid-triggered zincation allows the regioselective metalation of various chromones and quinolones. In the absence of MgCl(2), a C(3) zincation is observed, whereas in the presence of MgCl(2) or a related Lewis acid, C(2) zincation occurs. Applications to a natural flavone, isoflavone, and quinolone are shown.
Subject(s)
Chromones/chemistry , Flavones/chemical synthesis , Isoflavones/chemical synthesis , Lewis Acids/chemistry , Quinolones/chemistry , Zinc/chemistry , Biological Products/chemical synthesis , Chromones/chemical synthesis , Quinolones/chemical synthesis , StereoisomerismABSTRACT
Cyclic enol phosphates were magnesiated by a halogen/magnesium exchange reaction or deprotonation using TMP-derived magnesium amide bases. The resulting magnesium reagents react readily with a wide range of electrophiles like allyl bromides and acid chlorides or can be used in Pd-catalyzed cross-coupling reactions. Several optically pure enol phosphates were prepared starting from readily available d-(+)-camphor derivatives.
Subject(s)
Cycloparaffins/chemical synthesis , Halogens/chemistry , Magnesium/chemistry , Phosphates/chemical synthesis , Camphor/chemistry , Catalysis , Cycloparaffins/chemistry , Indicators and Reagents/chemistry , Phosphates/chemistry , Protons , Structure-Activity RelationshipABSTRACT
A broad range of functionalized aryl- and heteroarylzinc reagents were prepared via directed zincation of sensitive and moderately activated aromatics and heteroaromatics using TMPZnCl.LiCl under various reaction conditions. Diverse sensitive functional groups such as a nitro group, an aldehyde, an ester, and a nitrile are readily tolerated and are compatible with high metalation temperatures. Furthermore, the resulting zinc organometallics display an excellent reactivity toward various classes of electrophiles providing functionalized aromatics and heteroaromatics in high yields.
ABSTRACT
Successive regio- and chemoselective metalations of chloropyrazines using TMPMgCl x LiCl and TMPZnCl x LiCl furnish, after trapping with electrophiles, highly functionalized pyrazines in high yields. Application to a synthesis of coelenterazine, a bioluminescent natural product in jellyfish Aequorea victoria, in nine steps (9% overall yield) is reported.
Subject(s)
Imidazoles/chemical synthesis , Organometallic Compounds/chemistry , Pyrazines/chemistry , Pyruvaldehyde/chemical synthesis , Animals , Imidazoles/chemistry , Pyrazines/chemical synthesis , Pyruvaldehyde/chemistry , Scyphozoa/chemistryABSTRACT
A wide range of functional aryl and heteroaryl zinc reagents have been efficiently prepared via regio- and chemoselective zincation using TMPZnCl.LiCl and microwave irradiation. Sensitive functional groups like esters are compatible with the high temperatures of the reactions. The resulting zinc species undergo a number of subsequent reactions, providing highly functionalized aromatics and heteroaromatics in high yields.