Halides, aldehyde cross-coupling reactions

Of interest also is the aqueous Reformatsky cross-coupling reaction between a-halo ketones or aldehydes and carbonyl compounds in the presence of zinc, tin and indium. Like the Barbier-type reactions, indium was found to be the most efficient metal and it strongly reduced undesirable side reactions such as the reduction of the halide [134]. As usual in aqueous reactions implicating carbonyl compounds, lanthanum(III) triflate promoted the reaction [146]. 

CROSS-COUPLING REACTIONS OF ALDEHYDES WITH ACTIVATED HALIDES 251... 

Other approaches to trisubstituted aikenes via organoboranes involve alkynyltrialkyl borates, alkenyltrialkyl borates or the cross-coupling reaction of alkenylboronic acids with alkyl halides. Both ( )- and (2)-l,2-disubstituted alkenyl bromides can also be prepared by the methodology shown in eq 7. The boron trifiuoride etherate-mediated 1,4-addition of 1,2-disubstituted alkenylboronates affords y,5-unsaturated ketones (eq 9). The boronates can also be converted into chiral enoiborates for the enantioselective addition to aldehydes. ... 

The dioxaborole (97), formed from catecholborane and ethojqracetylene, undergoes a Pd-catalysed cross-coupling reaction with aryl or benzyl halides RX to give the vinyl ethers (98). Since these vinyl ethers can readily be hydrolysed to aldehydes (99), the overall sequence provides an efficient method for converting halides into aldehydes with two more carbon atoms. Also on the subject of boronic acid chemistry, a number of syntheses of the useful intermediates (100) have been published. ... 

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