Dibenzyl derivatives

The methylation of N-methyl derivatives of maleic hydrazide gives in general O-alkylated products. The opposite results are obtained with benzyl halides as alkylating agents. In this case the O-benzyl derivative (71) is formed, which is then further benzylated to the lV,0-dibenzyl derivative (72). When ethyl chloroacetate is used, the direction of alkylation is dependent on pH. At pH above 8, O-alkylation occurs at pH below 8, N-alkylation takes place exclusively in neutral and acidic solutions only IV-alkylated products are formed. 

Examples 2 and 3 above produce dibenzyl derivatives from primary amines. 

Dibenzyl phosphoramidates have been prepared from amino acids and the j)hos-phoryl chloride, (Bn0)2P(0)Cl. ° A diphenyl phosphoramidate has been prepared from a glucosamine it is converted by transesterification into a dibenzyl derivative to facilitate cleavage. ... 

Pd-C, 4.4% HCOOH, CH3OH, 25°, 10 h, 80-90% yield. The cleavage of benzylamines with H2/Pd-C is often very slow. Note in example 1 above that one of the benzyl groups can be selectively removed from a dibenzyl derivative. 

Recently reported289 is an analogous reaction involving the acid-catalyzed cyclization of (lZ,3 ,5Z)-l,6-diphenylhexa-l,3.5-triene-l,6-diamine (14) in refluxing toluene to 2,7-diphenyl-3//-azepine (15). The l,6-bis(4-tolyl) and 1,6-dibenzyl derivatives behave similarly, but give substantially lower yields (14-18%). 

Benzyl radical, C6H5CH2, and its deuterated analogues (C6H5CD2, CfiDsCHz) were obtained by vacuum thermolysis of dibenzyl derivatives or by pyrolysis of the corresponding benzyl bromides (17) (Baskir, 1989). 

Treatment of the 0,0-dibenzyl derivative of norneoenactin with 10% Pd/C in MeOH under hydrogen atmosphere resulted in the rapid deprotection (within 1 h) of the starting material. However, reduction of the benzyl ether functionality, without the concomitant hydrogenolysis of the N-O bond, required fine tuning of the conditions. When the hydrogenolysis was carried out using 20-25 mol % of 10% Pd/C at 20 or 30 mM concentrations for 22-31 hours, a... 

Thanks are due to the Editor of this volume for suggesting the similarity of N,N-disubstituted carbamoyl nitrites to the a-amino nitrite esters discussed above. When N,N-diphenyl carbamoyl chloride was refluxed with sodium nitrite in acetonitrile solution for 24 hours, N-nitrosodiphenylamine was produced in quantitative yield (M. Nakajima and J.-P. Anselme, unpublished results). The N,N-dibenzyl derivative underwent a similar reaction with nitrite. The mechanism shown in Fig. 13 was postulated to account for these transformations. 

Structure 190 has been converted into key intermediates 191a and 191b via bromination, cyanide displacement, and benzylation (Scheme 18). Cyclization of 191 occurs upon reduction of the nitro group to give 192 <2004BMC3187>. The A, iV -dibenzyl derivative of 190 leads to similar products <2004JME3187>. 

Bridged oxazinooxazine 153 forms a complex with Ni(n) <2001JOM(630)67>. Complexes are also observed with Pb(ll), wherein the ligand is isomerized to the dihydroxydiimine form, and with Cd(ll), in which case a mixture is formed, with the ligand present in all three tautomers. The formation of 152 by catalytic hydrogenolysis of its 1,5-dibenzyl derivative has been reported (Equation 183) <2006S1093>. 

Stoichiometric oxidation using TBHP and a 2 1 Ti tetraisopropox-ide-diisopropyl tartrate system can kinetically resolve racemic dialkyl-amino alcohols (Scheme 46) (106). The efficiency, which ranges from 0-95% ee, is largely dependent on the substrates. When methyl groups or polymethylene rings are used, the reaction proceeds to afford greater than 90% ee, whereas iV.iV-dibenzyl derivatives show little or no resolution. Use of natural (2/ ,3/ )-diisopropyl tartrate consistently gives R amino alcohols. 

Dibenzyl derivatives 208 (R = Ph) are converted into pyrroloanthrones 210 (R = Ph) under milder conditions (8ICLI789). The ring contraction of anthrapyridonyl diazonium salts 211, which takes place in water in the presence of alkaline agents, leads to 2-carboxypyrroloanthrone 212 (77KGSI103). 

In the first attempt to prepare disaccharide 139, the dibenzyl derivative 143221 with a nonparticipating C-2 benzyloxi group was selected as donor. However, a mixture of both disaccharides was obtained in low yield, with predominance of the ot-anomer. 

Bis[alkoxycarbonyl] telluriums are thermally rather stable and are not very sensitive to moisture. The compounds can be stored in the refrigerator under argon for weeks without decomposition. The dibenzyl derivative is the least stable of these compounds it decomposes within a few hours after isolation. These yellow to orange liquids with a characteristic odor that is not as offensive as the odor of dialkyl telluriums produce black stains on the skin a few hours after contact. 

Lewis and Petisce [44] have investigated PET reactions between a number of cyano aromatic electron acceptors and electron donating methyl aromatic systems. Botb substitution as well as dimer products have been observed depending on the electron affinity of the acceptor [44,45]. When weak electron acceptors, e.g. m-dicyanobenzene and benzonitrile, were used dibenzyl derivatives were formed predominantly. In contrast, strong electron acceptors produced predominantly substitution products. For example, use of tetracyanobenzene with p-xylene produced predominantly in-cage substitution product while use of m-dicyanoben-... 

Alkylation of amines and amides with benzylic halides is an early and useful method for the protection of amines and amides. Primary amines can alkylate twice to give the W,N-dibenzyl derivative, but severe steric congestion prevents quatemisation [Scheme 8.199].410... 

So far, dibenzyl derivatives remain the only hydrocarbon source for hydrocarbon elimination reactions, especially since... 

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