Alcohols allyloxycarbonyl

Allylamines are difficult to cleave with Pd catalysts. Therefore, amines are protected as carbamates, but not as allylamines. Also, allyl ethers used for the protection of alcohols cannot be cleaved smoothly, hence alcohols are protected as carbonates. In other words, amines and alcohols are protected by an allyloxycarbonyl (AOC or Alloc) group. 

PdCl2(Ph3P)2, dimedone, THF, 95% yield. This method is also effective for removing the allyloxycarbonyl group from alcohols and amines. 

F.Guibf and Y. Saint M Leux, The allyloxycarbonyl group for alcohol protection Quantitative removal or transformation into allyl protecting group via w-allyl complexes of palladium, Tetrahedron Lett. 22 3391 (1981). 

Alcohols are protected as allyl ethers, which are difficult to cleave with the Pd catalyst and deprotected by other methods [149]. Alcohols are conveniently converted to allyl carbonates 334 by treatment with allyl chloroformate (333). The allyl carbonates are deprotected using HCO2H [150], and HSnBu3 [151]. This method is called the AOC (allyloxycarbonyl) method. Phenols are protected as allyl phenyl ethers, which can be cleaved with HSnBu3 [152]. 

Diallyl dicarbonate was used for the allyloxycarbonyl protection of amino compounds including amino acids, amino sugars and nucleosides. Except for the reaction with amino acids, the reagent does not require an additional base, and the only by-products, allyl alcohol and carbon dioxide are both volatile. For example, N-allyloxycarbonyl glucosamine was obtained analytically pure by simple evaporation of the reaction mixture. 

The use of the water-soluble sodium azide as the allyl scavenger allowed the cleavage of allyloxycarbonyl-protected alcohols to occur under essentially neutral... 

This efficient and unexpensive methodology thus allows the removal of allyl and allyloxycarbonyl groups from various substrates and the particularly mild conditions are compatible with polyfiinctionalized molecules. Moreover, both Pd(0) catalyst and N-allyl diethylamine by-product are easily separated from the free alcohols, amines and carboxylic acids which are recovered in almost pure form. 

A second very mild procedure involves the Pd-catalysed extrusion of CO2 from allyloxycarbonyl (Aloe) derivatives (see section 4.8.6) which in turn, are simply made by acylation of an alcohol with allyl chloroformate in the usual way. Our example shows a double allylation in the presence of the sensitive l,l,3 3-tetra-isopropyldisiloxane-l,3-diyl group [Scheme 4.235]." ... 

The use of the water-soluble sodium azide as the aUyl scavenger aUows the cleavage of allyloxycarbonyl-protected alcohols to occur under essentially neutral conditions [34]. It has been shown that the phosphines (t-Bu- C5H4) P(C5H4-m S03Na)3 (n= 1, 2) are more efficient than TPPTS in the deprotection of long alkyl chain... 

A new Pd -catalysed deprotection of allyloxycarbonyl derivatives of alcohols cf. 6,174) involves exchange with carboxylic acids, as shown in equation (13). ... 

Palladium-catalyzed Deprotection Processes. Several palladium-catalyzed and mild methods for the deprotection of various functional groups have been developed. For example, a system for the conversion of hydrazones into the corresponding carbonyl compounds that is catalytic in both Pd(OAc)2 and SnCl2 has been reported, as has a procedure for the Pd(OAc)2-catalyzed cleavage of allyloxycarbonyl (Alloc) protected alcohols. ... 

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