Amine scavenging

Scheme 7.129 Efficient amine-scavenging utilizing a polystyrene aldehyde scavenger.

B. Linclau, A. K. Singh, D. P. Curran, Organic-Eluorous Phase Switches A Fluorous Amine Scavenger for Purification in Solution Phase Parallal Synthesis , J. Org. Chem 1999, 64, 2835. 

Similarly, Xu has applied a combination of supported bases and amine scavengers for the decoration of both phenolic compounds [93] and various alkaloids... 

Two complementary procedures have been developed for alkylation of secondary amines [11] - both of which involve the use an excess of amine to drive the reaction to completion. The remaining amine was removed from the required tertiary amine using a polymer supported isocyanate 5 as a nucleophilic scavenger (under thermodynamic control) (Table 1 entry 2). The use of this amine scavenger has subsequently been applied in the purification of urea-based libraries prepared by solid-phase organic synthesis [12],... 

Linclau B, Sing AK, Curran DP. Organic-Fluorous phase switches a fluorous amine scavenger for purification in solution phase parallel synthesis. J Org Chem. 1999 64 2835-2842. Parlow JJ. Polymer-assisted solution-phase chemical library synthesis. Curr. Opin. Drug Discov. Devel. 2005 8 757-775. 

Isocyanates have traditionally been a highly utilized amine scavenger. Kaldor and coworkers first reported the polystyrene-based isocyanates [lc] since this... 

Scheme 8.2 Utilization of PS-isocyanate for amine scavenging in Triazolo pyrimidine library synthesis.

Scheme 8.6 Utilization of supported aza-lactone for amine scavenging.

Scheme 8.12 Brase s synthesis of supported diazonium salts for amine scavenging.

Zhang and coworkers workers have also demonstrated the use of F-add chlorides alongside the concurrent use of the corresponding conventional resin-bound scavengers in the synthesis of a small library of sulfonamides with both primary as well as secondary amines. Scavenging was almost complete (<2% amine remained) with the use of F-add chlorides, while a substantial amount remained in the use of resins. After 24 h, amines were scavenged by the fluorous reagents, while 3-12% amines remained unquenched when resins were used (Scheme 8.20)... 

Scheme 8.20 Zhang s utilization of F-acid chlorides and F-isocynates for amine scavenging in comparison studies.

Representative amines scavenged in the synthesis of demonstration sulfonamide library Scheme 8.28 Soluble oligomeric sulfonyl chloride (OSC). 

Amine scavengers have been one of the most developed and widely used to remove a range of electrophiles on several different platforms. Traditionally developed on a polystyrene bead, amine scavengers have been utilized in natural products or library synthesis to yield high purity via a facilitated protocol. In 2005, Liu reported the use of a polystyrene-bound amine scavenger for the removal of excess aldehydes to provide imidazole derivatives in high purity without the need for classical purification (Scheme 8.30) [42]. 

In 2002, Ley reported the application of resin-bound reagents and polymers towards the synthesis of carpanone [57]. In the final steps towards carpanone, a resin-bound Co(salen) catalyst was used to give the desired intermediate along with the formation of a small amount of aldehyde by-product. To remove this byproduct, a resin-bound tris-amine scavenger was used, yielding the desired product in high purity (Scheme 8.42). 

Isocyanates can be determined by indirect titration of dibutylamine or by GC determination of this reagent, after reaction 39 (X = O R = R" = Bu) goes to completion. A variation of this procedure for isothiocyanate insecticides and other formulations consists of treating a solution in acetonitrile with excess primary amine, scavenging the excess amine with carbon disulphide, yielding a dithiocarbamate and determining the concentration by a 3-step titration with Cu(II) in acetonitrile... 

Hindered amine Light stabilizers Hindered amine scavenges radictils which are produced by light. This effect may be expltiined by the formation of nitroxyl radictils... 

Amine scavenger—thermosetting Methyl vinyl United States 3,820,290 1974 Norton... 

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