Allyl bromide Benzophenone

Alkyl-bromide (bzw. Allyl-bromid) sowie Ketone reagieren mit dem aus Benzophenon-methylimin und Lithium-diisopropylamid gebildeten l,l-Diphenyl-2-aza-allyl-lithium un-ter Substitution zu l-(Diphenylmethylen-amino)-alkanen bzw. l-(Diphenylme-thylen-amino)-2-hydroxy-alkanen, deren saure Hydrolyse 1-Amino-alkane bzw. 1-Ami no-2-hydroxy-alkane ergibt1. 

When treated with benzoic acid in the presence of triphenylphosphine and diethyl azodicarboxylate, benzophenone oxime gave a high yield of f -benzoylbenzanilide (14), formed via rearrangement of the intermediate 0>benzoyloxime (15). Reaction of p>medioxyaGetophenone oxime with l,rsubstituted derivative (l ), whereas in the presence of allyl bromide... 

In all cases it was reported that the trifluoromethyl group enhances the interaction in the prochiral ion pair, resulting in higher ee. The exception appears to be the asymmetric synthesis of a-amino acids via alkylation of the benzophenone Schiff base of glycine alkyl esters with allyl bromide, which produced a 56% ee with the trifluoromethyl-substituted catalyst compared to 66% with the unsubstituted catalysts TY-benzylcinchoninium chloride (3) or TY-benzylcinchonidinium chloride (4) (eq 5). ... 

Coldham has reported an application of this approach to provide enantioen-riched derivatives of 1,2-diamines, as demonstrated by the conversion of 49 to 50 (Scheme 14) [39]. The substituted imidazoline intermediate was obtained with an er of 92 8 on reaction with benzophenone while reaction with allyl bromide gave racemic product An interesting aspect of Coldham s study is the fact that the yield in the initial lithiation appears to be related to the rotational con-former of the Boc group which provides a complex which orients the base to remove the pro-S proton selectively. 

A comparison was made between the results of reactions of this allylic Grignard reagent and those of one-step Barbier reactions of allyl bromide and magnesium with three different substrates, i.e. benzophenone, acetophenone and carbon dioxide. 

Table 2.3. Comparison of the yields of reactions of allyl bromide and magnesium with benzophenone, acetophenone or carbon dioxide in the one-step and two-step reaction [41]...

Preparation by catalytic hydrogenation of 3-allyl-4-hydroxy-benzophenone (SM). SM was obtained by reaction of allyl bromide with 4-hydroxybenzophenone in the presence of potassinm carbonate, followed by Claisen rearrangement of the 4-(allyloxy)benzophenone so formed [168],... 

Preparation of 0-Allyl-N-(9)-anthracenylmethylcinchonidinium Bromide as a Phase Transfer Catalyst for the Enantioselective Alkylation of Glycine Benzophenone Imine tert-Butyl Ester. 

Alkylation and deprotection of N-protected aminomethylphosphonate esters 6 are shown in Scheme 6. The nitrogen is protected as the imine derived from benzophenone or a benz-aldehyde, and a variety of conditions are used for deprotonation and alkylation (Table 2). The benzaldehyde imine of aminomethylphosphonate can be deprotonated with LDA and alkylated with electrophilic halides (entries 1 and 2). For the best yields, saturated alkyl bromides require an equivalent of HMPA as an additive. 36 Allylic esters can be added to the carbanion with palladium catalysis (entries 3-7). 37,38 For large-scale production, phase-transfer catalysis appears to be effective and inexpensive (entries 8-12). 39,40 ... 

PREPARATION OF 0-ALLYL-N-(9-ANTHRACENYLMETHYL) CINCHONIDINIUM BROMIDE AS A PHASE TRANSFER CATALYST FOR THE ENANTIOSELECTIVE ALKYLATION OF GLYCINE BENZOPHENONE IMINE tert-BUTYL ESTER (4S)-2-(BENZHYDRYLIDENAMINO)PENTANEDIOIC ACID, 1-tert-BUTYL ESTER-5-METHYL ESTER... 

Proof for single-electron transfer in reactions of allyl- and crotylmagnesium bromide with benzophenone had been reported a few years before, in 1988, based on measurements of carbonyl carbon kinetic isotope effects (which were nonexistent) and substituent effect techniques [65]. Doubt about the correct interpretation of the observed phenomenon was discussed earlier in this chapter (see p. 237 [13]). 

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