Organolead reagents

Halostibines, Dihalostibines, and Related Compounds. Alkyl dichi oro- and alkyldibromostibines are readily prepared by the alkylation of the corresponding antimony trihaUde with an organolead reagent (67,104) ... 

The reaction has been carried out on an optically active a-methoxy organolead reagent and shown to proceed with retention (equation II). 

Palladium Cross-coupling with Organolead Reagents 412... 

The mildness of the conditions of reaction and the regioselectivity of the /V-arylation of imidazoles allowed the A-arylation of the azolic nitrogen of a protected histidine 87, even with the organolead reagent 88 derived from tyrosine, thus realizing the link between two aminoacid derivatives moieties (Equations (89) and (90)).1... 

Cross-coupling reactions between iodonium salts and organolead reagents can be catalyzed by palladium (Equation (107)).121 These reactions required 2 equiv. of base. In this system, homocoupling of the reagent could not be completely suppressed (Ar-Ar, 10-20%), and the reported yields for the products of the heterocoupling pathway (Ar-Ar ) were moderate (62-75%). 

This reaction was used in a short high-yielding synthesis of the alkaloids ( )lycoramine,15 156 ( )Q methyljoubertiamine and ( )mesembrine. All these syntheses involved in the key step the selective high-yielding arylation of alkyl 4-oxocyclohex-2,3-ene carboxylates (72) with organolead reagents. 

P-Dicarbonyl compounds generally reacted with heteroaryllead reagents to afford the a-aryl derivatives in synthetically useful yields. However, in the reaction of 2-thienyllead triacetate with 2-ethoxycarbonylcyclopentanone (86), the C-arylation product was observed in a low yield (9%), together with the presence of a dimer resulting from a radical oxidative coupling induced by the organolead reagent. Use of 2-thienyllead tribenzoate, a weaker oxidant, restored the classical reactivity. When the reaction was performed in pyridine as solvent, the arylation product, the 2-(2-thienyl)cyclopentanone derivative, was obtained in 76% yield. 

Two new organolead reagents (173) and (174) have been described. Both anions are good nucleophiles, reacting with a wide range of... 

It was suggested that the lead-promoted reaction involves the formation of an active divalent organolead reagent with the aid of the ammonium bromide, present in solution. A possible structure for the intermediate could be the following ... 

Arylation of organolead reagents to 1,3-keto ester, oxidative dearomatization reaction, and intramolecular Diels-Alder reaction were applied as the key reactions to successfully construct the tetracyclic structure of natural product Maoecrystal V and two consecutive quaternary carbons. 

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