Deallylation, ethers

A similar process can be efficiently used for the deallylation or debenzylation of the corresponding ethers 52 and 53, just using water as the quenching reagent after the lithiation process. Some examples giving alcohols or phenols 54 are included in Scheme 17 . 

The 4-amino group of 31 was selectively acetylated under acidic conditions using acetic anhydride (1 equiv.) and methanesulfonic acid (1 equiv.) in acetic acid and f-butylmethyl ether to give 32. Deallylation of 32 using 10% Pd/C in the presence of ethanolamine in refluxing ethanol proceeded as before to afford 1, which was converted to the phosphate salt in 70% yield with high purity (99.7%). The overall yield of 1 from epoxide 23 was 35-38%. 

The benzylidene derivative (94) has been converted into the alcohol (95) [97, 98] using the diborane — trimethylamine — aluminium chloride reagent [99] and into the diol (96) [95, 100, 101]. Veyrieres has converted methyl P-lactoside (and the corresponding allyl lactoside) into the 3-O-allyl ether (97) in good yield [102] by alkylation of the dibutylstannylene derivative in the presence of tetrabutylammonium iodide [103, 104], and this was converted into the alcohol (98) and the triol (99) [105]. Veyrieres [106] has also converted (97) into the per-p-bromobenzyl derivative and deallyl-ated the product to give a derivative with a free 3 -hydroxyl group. The diol (100) [107] has been converted by the stannylation procedure [108, 109] into the alcohol (101) [110, 111]. The partially acetylated benzyl P-lactoside (103) [101,112, 113] has been converted into the alcohol (104) via the orthoacetate [113]. 

The methyl 3 -0-allyl-P-lactoside (97) prepared by Veyrieres by the allylation of the dibutylstannylene derivative in the presence of tetrabutylammonium bromide [102] was converted into the per-p-bromobenzyl ether and deallylated to give (306). This was condensed "[106] with the chloride (282) in the presence of silver triflate to give a tetrasaccharide in 68 % yield. This was far superior to the condensation of the oxazoline (294) with (306) which gave a very low yield (9%) of tetrasaccharide. Depro-... 

Olefin isomerization catalyzed by ruthenium alkylidene complexes can be applied to the deprotection of allyl ethers, allyl amines, and synthesis of cyclic enol ethers by the sequential reaction of RCM and olefin isomerization. Treatment of 70 with allyl ether affords corresponding vinyl ether, which is subsequently converted into alcohol with an aqueous HCl solution (Eq. 12.37) [44]. In contrast, the allylic chain was substituted at the Cl position, and allyl ether 94 was converted to the corresponding homoallylic 95 (Eq. 12.38). The corresponding enamines were formed by the reaction of 70 with allylamines [44, 45]. Selective deprotection of the allylamines in the presence of allyl ethers by 69 has been observed (Eq. 12.39), which is comparable with the Jt-allyl palladium deallylation methodology. This selectivity was attributed to the ability of the lone pair of the nitrogen atom to conjugate with a new double bond of the enamine intermediate. 

Deallylation. Ally ethers are cleaved by r-BuLi via an 5 2 process. ... 

Deallylation. Allyl aryl ethers are converted to phenols using electrogenerated nickel. 

Deallylation. Allyl aryl ethers suffer cleavage electrochemically. PdCl2-bipyridine is the catalyst. Under such conditions O — C allyl transfer within 2-allyloxybenzalde-hydes takes place. 

Deallylation. The combination with BuLi forms Cp2Zr which is effective for cleavage of allyl ethers and amines. The reagent shows a higher reactivity towards ally ethers. 

O-Dealkylation s. Ethers, cleavage, O-Detritylation N-Deallylation 32, 997 Deamination... 

The 0-deallylation of allyl ethers is easily accomplished in virtually quantitative yield by allowing a solution of the ether and 1 molar equiv of f-BuLi in pentane to stand for 1 h at room temperature (eq 45). Allyl ethers derived from primary, secondary, and tertiary alcohols as well as those derived from phenols are cleaved cleanly and in high yield. 

In an extension of these studies, a new synthesis of indole derivatives was reported (Mori and Ban, 1976a) from 2-chloro-N-methyl-lV-allylaniline (XLll) by refluxing in ether for several hours with tetrakis(triphenyl-phosphine)nickel [Ni(PPh3)4]. The latter was prepared in situ to prevent deallylation. After oxygen was bubbled through the solution to convert PPhs into O <— PPhs for easy handling, the 1,3-dimethyl indole (XLIII) was obtained in a yield of 45.6%. 

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