Protecting moieties trifluoroacetyl

From the synthetic viewpoint, a particularly interesting trifluoroacetylation reaction of simple vinyl ethers was reported first by Hojo et al in 1976 [73] The scope and limitation of this particular reaction were elaborated intensively, the reaction proved to be of general applicability with practically no restrictions on substituents of the vinyl ether moiety 9] (equation 34) This general validity is particularly beneficial because a trifluoroacetylated vinyl ether is the synthetic equivalent of a specifically protected tnfluoromethyl-substituted 1,3-dicarbonyl compound 19], thus the reaction provides access to a broad spectrum of variously substituted synthetic building blocks with selective reactivities on each carbon acceptor (a) and donor (d) center (equation 35) Obviously, such building blocks can react as heterodiene systems m cycloaddition reactions [< 74] or can be treated with a wide variety ot 1,2 or 1 3-dinucleophihc species to give any desired tnfluoromethyl-substituted carbocychc or heterocyclic system [8 75] Treatment of simple vinyl ethers with an excess of trifluoroacetic anhydride at elevated temperature leads to doubly acylated products [76] Comparable acylation reactions occur with vinyl thioethers [73], and the mesoiomc l,3-oxathiol-4-ones show, at least in a formal sense, similar behavior [77] (equation 36)... 

Conversion of daunorobicin hydrochloride to 4 -epi-doxorubicin hydrochloride employing the trifluoroacetyl moiety for the 3 -amino group protection ... 

Trifluoroacetic acid anhydride reacts exclusively with the amino moiety of the amino alcohol 5, The trifluoroacetyl group has long been known as a valuable protecting group. ... 

The synthesis of the porphyrin moiety began with 5,15-bis(4-acetami-dophenyl)-10,20-bis(4-methylphenyl)porphyrin (28) (12,32) which upon treatment with concentrated aqueous HCl gave 5,15-bis(4-aminophenyl)-10,20-bis(4-methylphenyl)porphyrin in 96% yield (12,13). Protection of the diamino-porphyiin with trifluoroacetic anhydride furnished the bis-trifluoroacetylated porphyrin in 98% yield (6, 13). Partial hydrolysis of this compound provided monoaminoporphyrin 14 (Scheme I) in 60% yield. 

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