Trichloroacetimidate Reagents

Aldrich ChemFiles 2007, 7.3, 4.

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

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  1. Greene, T. W.; Wuts, P. G. M. Protective Groups in Organic Synthesis, 3rd ed.; John Wiley & Sons: New York, 1999.
  2. Honda, T. et al. Org. Lett. 2004, 6, 87. Attempted allylation with allyl bromide under basic conditions did not provide the desired compound.
  3. Goekjian, P. G. et al. J. Org. Chem. 1999, 64, 4238.
  4. Krüger, J.; Hoffmann, R. W. J. Am. Chem. Soc. 1997, 119, 7499. Attempted allylation under basic conditions resulted in silyl migration.
  5. Ichikawa, Y. et al. Org. Lett. 2006, 8, 5737.
  6. Manaviazar, S. et al. Org. Lett. 2006, 8, 4477.
  7. Keck, G. E. et al. Org. Lett. 2006, 8, 3667.

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