Oxazoline, chirality

SCHEME 128. Catalytic enantioselective Kharasch-Sosnovsky reaction catalyzed by different Cu-oxazoline chiral complexes... 

RLi (R = alkyl, aryl, vinylic), sparteine or bis(oxazolines) (chiral)... 

An enantioselective reaction of a-hydroxymethyl acrylates, using a bis-oxazoline chiral catalyst, gives the equivalent of formaldehyde aldol products in good yield and ee.m... 

Oxazolines Chiral Building blocks, Auxiliaries and Ligands... 

Perhaps the simplest of the isoquinoline alkaloids is salsolidine. It has been synthesized by asymmetric alkylation of 6,7-dimethoxytetrahydroisoquinoline using either a formamidine ° or oxazoline chiral auxiliary. Scheme 25 illustrates the recently published Organic Syntheses preparation of salsolidine on a 5 g scale. It is of interest to note that, in this and all subsequent examples of asymmetric alkylation of tetrahydroisoquinolines, formamidines derived from L-valine afford (IS)-tetrahydroisoquinolines, while oxazolines derived from L-valine afford the (lf )-enantiomer. The reason is simply the opposite orienta-... 

The extraction concept is also applicable to sophisticated syntheses of fine-chemicals as recently shown by Ohe, Uemura and co-workers [35], They prepared a novel amphiphilic phosphinite-oxazoline chiral ligand based on D-glucosamine. The corresponding palladium complex was an efficient catalyst for asymmetric allylic substitution reactions and could be recycled by simple acid/base extraction and reused in the second reaction without loss of enantioselectivity. 

In 1989. Kelly Rein began an investigation into the use of an oxazoline chiral auxiliary to elfect diastereosclcctive additions of Grignard reagents based tin the Scebach discovery. The initial effort 46 used an oxazoline auxiliary derived front valine ( laltle 5.3. entry 5), one that we had used previously in studies of asymmetric alkylations ol... 

The mechanism of the Stevens rearrangement has been reviewed. The key reaction in the total synthesis of ( )- and (+)-eupomatilone was an asymmetric [2,3]-Wittig rearrangement employing a bis(oxazoline) chiral ligand (Scheme 101). ... 

A study of chiral induction in the asymmetric [2,3]-Wittig rearrangement of allyl benzyl ether in the presence of a bis(oxazoline) chiral ligand [(5,5)-Box-r-Bu] has been reported (Scheme 45). °... 

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