Barbier/aldol reactions

Barbier/aldol reactions of enones. The iodo enone 1 on treatment with Sml2 (2 equiv.) in THF containing DMPU (10 cquiv.) undergoes reductive cyclization to the bicyclo[3.3.0]octane-3-one (2) in 70% yield. Such reductive cyclizations have been effected with a tin hydride. The advantage of the Sml2 reaction is that it proceeds... 

Simple enamines cannot be deprotonated directly at the a-position due to their low acidity, but starting from a-chloroenamines 685, a-lithioenamines 686991 have been prepared by chlorine-lithium exchange using an arene-catalyzed lithiation992. The treatment of compounds 685 with an excess of lithium and a catalytic amount of 4,4 -di-tert-butylbiphenyl (DTBB) in THF at —90 °C allowed the preparation of intermediates 686, which were trapped with a variety of electrophiles (Scheme 177). For aldol reactions, the arene-catalyzed lithiation has to be performed in the presence of aldehydes (Barbier conditions) at —40 °C. These adducts were transformed into a-hydroxy ketones after acid hydrolysis with hydrochloric acid or silica gel. 

Lantanides and Sml2 specifically in carbon-carbon bond formation or for functional group transformation (cyclization, Barbier type reaction, intramolecular coupling, aldol, Evans, Tishenco). 

Vinylogous Barbier reaction,4 Smlj (2 equiv.) can effect cyclization of the unsaturated iodo ketone 1 in THF containing DMPU (or HMPA) to give a bicyclic samarium enolatc (a) that can be trapped by an aldol reaction. 

Various reactions. The binary salt is a very useful reagent for promoting Barbier reaction, Mukaiyama-aldol reaction, Michael reaction, Mannich reaction, Diels-Alder reaction, as well as the reductive coupling of carbonyl compounds and of imines. 

Grignard was awarded the Nobel Prize in Chemistry in 1912 for his extensive work with organomagnesium compounds. He returned to the University of Lyons in 1919, where he succeeded Barbier as head of the department and continued his research. Grignard also conducted an extensive research program in the fields of terpenoid natural products, ozonolysis, aldol reactions, and catalytic hydrogenation and dehydrogenation. However, it is for his... 

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