Chlorine reaction with aldehydes

Post-reactions of polyacrylamide to introduce anionic, cationic, or other functional groups are often attractive from a cost standpoint. This approach can suffer, however, from side reactions resulting in cross-linking or the introduction of unwanted functionality. Reactions include hydrolysis, sulfoiiielliylatioii, melliylol formation, reaction with other aldehydes, transamidadon, Hoffman degradation, and reaction with chlorine. 

Allylmagnesium bromide, 41, 49 reaction with acrolein, 41, 49 5-Allyl-l,2,3,4,5-pentachlorocyclopen-tadiene, 43, 92 Allyltriphenyltin, 41, 31 reaction with phenyllithium, 41, 30 Aluminum chloride, as catalyst, for isomerization, 42, 9 for nuclear bromination and chlorination of aromatic aldehydes and ketones, 40, 9 as Friedel-Crafts catalyst, 41, 1 Amidation, of aniline with maleic anhydride, 41, 93... 

Aldehydes can be directly converted to acyl chlorides by treatment with chlorine however, the reaction operates only when the aldehyde does not contain an a hydrogen and even then it is not very useful. When there is an a hydrogen, a halogenation (12-4) occurs instead. Other sources of chlorine have also been used, among them S02Cl2 and r-BuOCl. The mechanisms are probably of the free-radical type. V-Bromosuccinimide, with AIBN (p. 912) as a catalyst, has been used to convert aldehydes to acyl bromides. 

The reaction of the unsaturated aldehyde 32 with cat. Cp2 VCl2/Me3SiCl/ Zn is conducted in THF to afford the cyclic alcohol 33 with excellent dia-stereoselectivity (Scheme 19) [21]. The transformation may be explained by 5-exo-cyclization of the corresponding radical anion, followed by chlorination. 

Our first entry to the use of porphyrins as dipolarophiles in 1,3-DC reactions involved the reaction of porphyrins with azomethinic ylides, generated in situ from a-amino acids and aldehydes, to yield chlorins and isobacteriochlorins (bisadducts) <99CC1767, 05JOC2306>. 

Few data are available on the electrophilic substitution of dibenzofurans containing more than one substituent. 1,4-Dimethyldibenzofuran affords, as expected, the 2-aldehyde on reaction with dichloromethyl methyl ether and tin(IV) chloride. " The nitration of 2,4-dimethyldibenzofuran has also been studied. Acetylation of 4-methoxy-7-nitro- and 8-nitrodibenzofuran occurs exclusively at the 1-position. Similarly, both 4,6- and 3,4-dimethoxydi-benzofuran undergo bromination and acetylation at the 1-position. The acetylation of 1,3-dimethyl-, 1,4-dimethyl-, and 2,4-dimethyl-7-methoxydibenzofuran have been studied the acetyl group enters the 8-position. The chlorination of 3,7-dichlorodibenzofuran has also been studied. ... 

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