Trichloroacetimidate Reagents

As described previously, trichloroacetimidates are also commonly employed as alcohol alkylation reagents, particularly when existing functionality is not acid sensitive.¹ Recent applications of allyl trichloroacetimidate include the synthesis of an allyl propargyl ether intermediate in the synthesis of the fused-ring alkaloid securinine,² preparation of fluorinated probes for protein kinase C (PKC),³ and in the formal synthesis of the oxocene target Laurencin (Scheme 1).⁴

Scheme 1. ( 678414 )

Likewise, 4-methoxybenzyl trichloroacetimidate has found extensive application for the protection of alcohols in the form of p-methoxybenzyl (PMB) ethers that are readily cleaved under oxidative conditions, typically dichlorodicyanoquinone (DDQ) or ceric ammonium nitrate (CAN). As shown in Scheme 2, 4-methoxybenzyl trichloroacetimidate was successfully applied in the selective preparation of chiral syn- or anti- diamines,⁵ as well as in independent syntheses of bryostatin intermediates (Scheme 3).^6,7

Scheme 2

Scheme 3

Materials

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References

1. Greene TW, Wuts PGM. 1999. Protective Groups in Organic Synthesis. https://doi.org/10.1002/0471220574

2. Honda T. 2004. Attempted allylation with allyl bromide under basic conditions did not provide the desired compound. . Org. Lett. 6(87):

3. Goekjian PG, Wu G, Chen S, Zhou L, Jirousek MR, Gillig JR, Ballas LM, Dixon JT. 1999. Synthesis of Fluorinated Macrocyclic Bis(indolyl)maleimides as Potential19F NMR Probes for Protein Kinase C. J. Org. Chem.. 64(12):4238-4246. https://doi.org/10.1021/jo9808876

4. Krüger J, Hoffmann RW. 1997. Substituted Oxocanes by Intramolecular Allylboration Reactions. Entry to an Efficient Synthesis of (+)-Laurencin. J. Am. Chem. Soc.. 119(32):7499-7504. https://doi.org/10.1021/ja970914u

5. Ichikawa Y, Ohara F, Kotsuki H, Nakano K. 2006. A New Approach to the Neoglycopeptides:? Synthesis of Urea- and Carbamate-TetheredN-Acetyl-d-glucosamine Amino Acid Conjugates. Org. Lett.. 8(22):5009-5012. https://doi.org/10.1021/ol0616788

6. Manaviazar S, Frigerio M, Bhatia GS, Hummersone MG, Aliev AE, Hale KJ. 2006. Enantioselective Formal Total Synthesis of the Antitumor Macrolide Bryostatin 7. Org. Lett.. 8(20):4477-4480. https://doi.org/10.1021/ol061626i