Reformatsky reactions intermolecular

The ability of Sml2 to reduce alkyl halides has been exploited in a number of carbon carbon bond-forming reactions. Radicals generated from the reduction of alkyl halides can be trapped by alkenes in cyclisation reactions to form carbocyclic and heterocyclic rings (see Chapter 5, Section 5.3), and the alkyl-samarium intermediates can be used in intermolecular and intramolecular Barbier and Grignard reactions (see Chapter 5, Section 5.4). The reduction of ot-halocarbonyl compounds with Sml2 gives rise to Sm(III) enolates that can be exploited in Reformatsky reactions (Chapter 5, Section 5.5) and are discussed in Section 4.5. 

Sml2 Reformatsky methodology is now sufficiently robust that Linhardt employed Reformatsky-type addition to carbon electrophiles in a solid-phase synthesis of C-sialosides (see Chapter 7, Section 7.3).146 The use of a-halo ketones in intermolecular Reformatsky reactions is less common and is typically restricted to simple coupling partners. For example, Ohta showed that... 

The intermolecular Sml2 Reformatsky reactions of a-haloamides have similarly received little attention however, Ohta showed that 7V,tV-dibenzyl-a-haloamides undergo efficient coupling with a range of aldehydes and ketones (Scheme 5.94).148... 

A second example is the intermolecular reaction of an ethyl a-bromo-a-fluoro-or trifluoromethylacetate (Eq. 77). With TMS-protected cyanohydrins, the Reformatsky reaction yields p-keto-y-butyrolactones. Sonication is essential for success. 

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