Benzyl Experimental Procedure

The Claisen method (c) furnishes the most convenient and practical procedure for the preparation of this ester. The materials are cheap, the experimental procedure simple, and the product obtained is free from objectionable traces of benzyl... 

Experimental Procedure 2.2.1. Photolysis of a Chromium Carbene Complex 2-Benzyl-4-benzyloxy-4-methyl-2,3,4,4a,7,7a-hexahydro-li/-cyclopenta[c]pyri-din-3-one [294]... 

Experimental Procedure 4.2.5. Ammonium Ylide Formation and Stevens Rearrangement Diethyl 2-Benzyl-2- [(ethoxycarbonyl)mefiryl](methyI)amino malo-nate [1241]... 

Polystyrene-bound allylic or benzylic alcohols react smoothly with hydrogen chloride or hydrogen bromide to yield the corresponding halides. The more stable the intermediate carbocation, the more easily the solvolysis will proceed. Alternatively, thionyl chloride can be used to convert benzyl alcohols into chlorides [7,25,26]. A milder alternative for preparing bromides or iodides, which is also suitable for non-benzylic alcohols, is the treatment of alcohols with phosphines and halogens or the preformed adducts thereof (Table 6.2, Experimental Procedure 6.1 [27-31]). Benzhy-dryl and trityl alcohols bound to cross-linked or non-cross-linked polystyrene are particularly prone to solvolysis, and can be converted into the corresponding chlorides by treatment with acetyl chloride in toluene or similar solvents (Table 6.2 [32-35]). 

No mention was made of other counterions being studied or substituent effects. If heterolytic cleavage had occurred, then benzyl ethyl ether would have been observed. Although no mention was made of the experimental procedure with regard to oxygen exclusion, oxidized phosphorus products were observed. 

Beak and Du [1007] performed the asymmetric alkylation of racemic dipole-stabilized dilithium reagents generated by benzylic metalation of 5.2 (X = H or n-BujSn) with s-BuLi (Figure 5.2). Sparteine 2.5 must be added to anionic species prior to the electrophile. These reactions are run in THF/fert-butyl methyl ether at -78°C. No asymmetric induction is observed when this experimental procedure is used for the alkylation of 4.2. 

Many different research groups have contributed to the collection of empirical data in Tables 6-21. In some cases where the results do not fit overall trends, there are differences between similar experiments due to troublesome experimental or structural variables. A few of the misfits are probably due to uncertain structural assignments, and many of the others correlate with experimental procedures in which the concentration of electrophilic byproducts or contaminants (lithium ion, hydroxyl groups, protic or Lewis acids) is not controlled. There are also some misfit cases among the reactions of unsymmetrical ketones, and in reactions where allylic, benzylic, or propargylic ylides are employed. However, the great majority of cases are well behaved and follow general patterns that are summarized in Table 22 and are discussed in the section on interpretation of stereoselectivity trends. 

Why is it not necessary for refi actionation of benzyl benzoate obtained in the above experimental procedure ... 

The isomeric 2-deoxy-2-C-methyl-pentonic acids (34) have been prepared by Lewis acid-catalysed aldol condensation of the thioester silyl ketene acetal (35) with 2,3-di-O-benzyl-D-glyceraldehyde either epimer can be obtained as the major product depending on the precise experimental procedure adopted. 

Design and execute an experimental procedure for separating benzyl alcohol (7) from methyl benzoate (8) by normal-phase column chromatography. 

Experimental procedure for the thermolysis of aryliodonium ylides. Preparation of 40 (Scheme 18.31) A suspension of 133 (1 mmol) and benzyl amine (1 mmol) in CH2CI2 (15 mL) was refluxed for 4-7 hours until a clear solution resulted and TLC showed the disappearance of the starting ylide. The solution was concentrated in a vacuum to half its volume, hexanes (10 mL) were added, and the precipitated yellow solid was filtered and washed repeatedly with hexanes. The amide 140 (mp 144-146°C) was obtained in 84% yield. An analytical sample was obtained by recrystalUzation from CH2Cl2-hexanes. 

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