ROMPGEL

The use of polymer-supported reagents in combinatorial chemistry has received much attention in recent years, and a polymer-supported acylating reagent (supported on a ROMPGEL) has been used for the synthesis of 1,2,4-oxadiazoles in solution, (see Equation 37), <2000CCHT131>. 

ROMPgels and Other Functional Metathesis-based Polymers... 

Tab. 8.3 ROMPgels and catalytic supports described by Hanson et al. and Bolm et al.

Future industrial prospects are suggested by the exceptionally diverse range of applications in which ROMP polymers have now been deployed. The impact of ROMPgel reagents was alluded to above. These and... 

Barrett AGM, Love AC, Tedeschi L (2004) ROMPgel-supported thiazolium iodide an efficient supported organic catalyst for parallel Stetter reactions. Qrg Lett 6 3377-3380... 

ROMPgel-supported thiazolium salts <2004OL3377> (ROMPgel = ring opening metathesis polymerization gel) and the effect of pressure on Stetter reactions in the synthesis of hindered aliphatic acyloins and 7-ketonitriles <2004HPR233> were also investigated. 

Barrett, A. G. M., Hopkins, B. T., Love, A. C., Tedeschi, L. Parallel Synthesis of Terminal Alkynes Using a ROMPgel-Supported Ethyl 1-Diazo-2-oxopropylphosphonate. Org. Lett. 2004, 6, 835-837. 

Barrett, A.G.M., Cramp, S.M., Hennessy, A.J. et al. (2001) Oxazole synthesis with minimal purification synthesis and application of a ROMPgel Tosmic reagent. Organic Letters, 3,271-273. 

Barrett and co-workers adapted ring-opening metathesis polymerization (ROMP) to prepare the ROMPgel TosMlC reagent 1621 (Scheme 1.414, p. 364). Thus copolymerization of the norbornene-derived formamide 1620 with norbor-nene in the presence of Grubbs s catalyst" gave 1621 in quantitative yield after dehydration. Aromatic aldehydes react with 1621 in the presence of a strong... 

Reactions of aromatic or heteroaromatic aldehydes 144 with a ROMPgel Tosmic reagent 143, available from the ring opening metathesis of 142, allowed the preparation of a small library of oxazoles 145 in high yields and with minimal purification <01OL271>. 

Polymer-supported TosMIC reagent 1612 has been described and employed in an oxazole synthesis involving minimal purification [1203]. ROMPgel TosMIC reagent 1612 was prepared from the corresponding polymeric formamide 1611 by dehydration with phosphoryl chloride in 100% yield. 1611 was obtained by ROM polymerization of 1610 in 100% yield [1203]. 

Many 5-aryl-l,3-oxazoles, bearing various functions at the aryl group, can be prepared in good yields of 68-90% and with high purities from aldehydes and ROMPgel TosMIC reagent 1612 they are purified only by filtration without any need for chromatography [1203]. This makes the method particularly well-suited for use in combinatorial chemistry. 

Later, Barrett created the term ROMPgel for linear polymers, which swell but do not dissolve in certain solvents because of solubility restrictions governed by the nature of the functional monomer used. Such ROMPgels were prepared with a variety of different functional groups including phosphines [3], allyl-boronates [25], a polymeric Tosmic reagent [26], naphthalenes, and biphenyls [27], alkylphosphonates [28], as well as anhydrides [29], some in a precipitation polymerization setup similar to the one described by our group. 

Scheme 17 Preparation of ROMPGELs and functional monomers used.

A precedent of this methodology can be found in the preparation of a ROMPgel support of activated Mosher ester (MTPA) as a means to performing the purification free synthesis of MTPA amides by the Barrett group. 

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