1.3- Oxazolidines — Reaction products formaldehyde

NIOSH has developed independent methodologies for acrolein and formaldehyde which recommend the use of reagent-coated adsorbent tubes to collect the aldehydes as stable derivatives. The formaldehyde sampling tubes contain Chromosorb 102 adsorbent coated with N-benzy-lethanolamine (BEA) which reacts with formaldehyde vapor to form a stable o) olidine compound. The acrolein sampling tubes contain XAD-2 adsorbent coated with 2-(hydroxymethyl) piperidine (2-HMP) which reacts with acrolein vapor to form a different, stable oxazolidine derivative. Acrolein does not appear to react with BEA to give a suitable reaction product. Therefore, the formaldehyde procedure cannot provide a common method for both aldehydes. However, formaldehyde does react with 2-HMP to form a very suitable reaction product. It is the quantitative reaction of acrolein and formaldehyde with 2-HMP that provides the basis for this evaluation. 

Amino-hydroxy-acids are easily converted into oxazolidine-4- or -5-carboxylic acids or tetrahydro-oxazine-4-carboxylic acids, depending on structure, by reaction with formaldehyde. Scheme 108 illustrates the reaction for threonine the product is isolated as a benzoate. 

A convenient and stereoselective, synthetic route was reported for the preparation of 3,7-disubstituted-l,2,5-trithiepanes 209 by the reaction of thiiranes with bis(trimethylsilyl)sulfide (HMDST) followed by intramolecular oxidative cyclization (14HAC678). In the reaction of substituted etha-nolamines with formaldehyde, the desired bis(oxazolidin-3-yl)methanes were prepared as a mixture of products, the ratio of the isomeric 3,8-dioxa-l,6-diazabicyclo[4.4.1]undecane 210 product present was dependent on the substituent on the ethanolamine (14CHE726). Whether the bis(oxazolidin-3-yl)methanes were isolated or the mixtures were taken on for further reaction, the subsequent product was formed exclusively. 

Dihydro-1,3,5-dioxazines are the reaction/condensation products of primary amines with 3 mol of formaldehyde. Although they release a higher quantity of formaldehyde than, for example, 1,3-oxazolidines and are therefore more effective than other formaldehyde releasing compounds they are not of practical importance as microbicides because of their limited stability and very pungent odour. 

N-formals. Highly effective donor forms of formaldehyde are obtained by its reaction with amines or amides. Depending on the starting product and the reaction conditions, there are a large number of reaction possibilities. Thus we have such nitrogen formals as hexahydrotriazines, imidazolidines, oxazolidines, bisoxazolidines, aminals and methylol compounds of amides. 

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