Allyl scavengers

Pd(Ph3P)4, pyrrolidine, 0°, 5-15 min, CH3CN, 70-90% yield. Morpholine has also been used as an allyl scavenger in this process. ... 

Pd(Ph3P)4, LiBH4, THF, 88% yield. NaBH4 can also be used as an allyl scavenging agent. ... 

Pd(Ph3P)4, 2-ethylhexanoic acid or barbituric acid (THF, 3 h, 93% yield). Tributylstannane can serve as an allyl scavenger. ... 

Another method for deallylation is the Pd-catalyzed transfer of the allyl group to reactive nucleophiles. Sodium 2-ethylhexanoate [141], morpholine [142], dimedone [143] and AA-dimethylbarbituric acid [144] are used as allyl scavengers. It is claimed that benzenesulfinic acid 331 or sodium toluenesulfinate are the best allyl scavengers [145]. 

The enolate formed in this process then condenses irreversibly with the r -allylpalladium species. At the outset, dimedone and A,A-dimethylbarbituric acid had been more specifically devisedP for the deprotection of allyl carbamates in solution or in solid-phaseP chemistry in which case the enolate species also forms by proton transfer from the (3-dicarbonyl allyl scavenger to the liberated amine but since then it has also been used for the deprotection of allyl carboxylic esters (see Section 2.2.1.1.3).P 1... 

Pd(Ph3P)4 and Bu3SnH will convert the Alloc group to other amine derivatives when electrophiles such as (B0C)20, AcCl, TsCl, or succinic anhydride are added. Hydrolysis of the stannyl carbamate with acetic acid gives the free amine. PhSiH3 also serves as an allyl scavenger in this type of transformation. ... 

The deprotection of aloe derivatives of secondary amines such as N,N-benzylme-thylamine under the above conditions gave a substantial amount of the undesired allylamine [32], However, the use of a 40-fold excess of diethylamine as the jr-allyl scavenger led to the desired benzylmethylamine in quite good yield (Eq. 9). The formation of the undesired allylamine was also suppressed using a fivefold excess of diethylamine in a butyronitrile/water system. N-Allyloxycarbamates derived from secondary amines, such as morpholine, piperidine, proline, and ephedrine, reacted under the above-mentioned conditions at room temperature within 15 min to give the parent amines in quantitative yields without formation of the undesired allylamine. 

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

When the N-alloc protecting group of primary amines such as benzylamine is cleaved rapidly imder these standard conditions in quantitative yields, the use of a 40-fold excess of diethylamine as the 7t-allyl scavenger or a five-fold excess of diethylamine in a butyronitrile/water system is necessary for the quantitative deprotection of aUoc derivatives of secondary amines. 

A new procedure for cleaving allyloxycarbonates using Pd(0), formed in situ from Pd(OAc)2 and trisodium tris(m-sulfophenyl)phosphine, with sodium azide as allyl scavenger, has been applied to a number of carbohydrate derivatives. ... 

The allyl ethers of phenols have also been deprotected using catalytic palladium(O) methodology. In this case, the improved leaving group ability of the phenoxide is sufficient to permit reliable deprotection using tri-n-butyltin hydride, sodium and lithium borohydrides, and phenyltrihydrosilane as the allyl scavengers." ... 

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