Hydroxy aldehydes from halo ketones

Alternatives which are more useful for /3-hydroxy carbonyl compounds are organometallic reagents. Organozinc reagents (67) react with aldehydes and ketones but not with esters so they can be made from a-halo esters. This, the Reformatsky reaction, has the advantage that the -halo esters are easily made (see Chapter 7). 

The selectivity of the Reformatsky reaction is apparent in Table 9.16, 26,327 taken from Heathcock s work, which shows the syn/anti selectivity for the hydroxy ester products (anti product 580 and syn product 581) resulting from reaction of a-haloesters with ketones and aldehydes. 27 Aldehydes generally show poorer selectivity than do ketones for formation of the anti product. 580. The bromozinc aldolate products from ketones were shown to equilibrate under reaction conditions but those from aldehydes did not. Generally, increasing the size of R in the a-halo-carbonyl derivative led to greater anti selectivity. 

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