O-Hydroxy aldehydes, metal derivatives

On a related front, the reactions of carbonyl compounds with metallated derivatives of 2-methylthia-zoline furnish adducts (85). Although the initial nucleophilic addition occurs smoothly with a wide variety of aldehydes and ketones, the intermediate 3-hydroxythiazolines (85) suffer thermal reversion upon attempted purification by distillation. Moreover, attempted cleavage of the corresponding 3-hydroxythia-zolidines, which are readily produced from (85) upon dissolving metal reduction (Al-Hg), leads to the formation of 3-hydroxy aldehydes only in simple systems numerous complications arising from dimerization, dehydration and retroaldol processes of the products usually intervene. Consequently it is necessary to protect the initial 1,2-adducts (85 R2 = H) as the corresponding O-methoxymethyl ether derivatives (86 R2 = MOM), which can then be easily transformed into protected 3-hydroxy aldehydes by sequential reduction and hydrolysis (Scheme 32).55... 

Within the last two decades, a number of chemical structures have been proposed as metal deactivators for polyolefins. These include carboxylic acid amides of aromatic mono- and di-carboxylic acids and N-substituted derivatives such as N,N -diphenyloxamide, cyclic amides such as barbituric acid, hydrazones and bishydrazones of aromatic aldehydes such as benzaldehyde and salicylaldehyde or of o-hydroxy-arylketones, hydrazides of aliphatic and aromatic mono- and di-carboxylic acids as well as N-acylated derivatives thereof, bisacylated hydrazine derivatives, polyhydrazides, and phosphorus acid ester of a thiobisphenol. An index of trade names and suppliers of a few commercial metal deactivators is given in Appendix A4. 

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