Chloroalkyl oxazolines

It was subsequently shown that carbanions generated from substituted a-chloroalkanenitriles [15] and alkyl a-chloroalkanoates [16, 17], chloroalkyl oxazolines [18, 19], chloroform [20], etc., although they are much less stable than the model sulfone carbanion, are able to react with nitroarenes to give the VNS products. 

OrganometaUic nucleophiles are also useful for MIRC cyclopropanation. The treatment of chloroalkyl oxazoline with LDA generated an oxazoline anion, which underwent cyclopropanation with alkenes through conjugate addition followed by intramolecular substitution [14]. The unsaturated Fischer carbene complex was also useful (Scheme 1.10) [15]. MIRC reactions to heterocyclic compounds have also been reported [16]. 

Yet another use for bis(oxazoline) ligands is in the synthesis of (a-chloroalkyl) boronates. " " As shown in Figure 9.71, the alkylboronate 240 was converted to the a-chloro derivative 241 in 86% ee through the use of ytterbium(lll) triflate-complexed phe-box 6. 

As base. Numerous reactions that are initiated by deprotonation have been conducted with KF-AI2O3. These include the synthesis of diaryl ethers, amines, and sulfides by nucleophilic aromatic substitutions, AJ-alkylation of 2,4-dinitrophenyl-hydrazones, condensation of 3-phenylisoxazol-5-one with aldehydes, and ring closure of /V-(w-chloroalkyl) carboxamides to afford 1,3-oxazolines and 1,3-oxazines. ... 

The syntheses of chiral C2-symmetric methylene-bis(oxazolines) and bi-oxazolines of type 6 and 8 are summarized in Schemes 10 and 11 [25]. Using the well-established three-step sequence - amide formation, conversion to the bis(2-chloroalkyl)amide, and subsequent base-induced cyclization [26] - various derivatives were prepared in good overall yields. Alternatively, these ligands may be synthesized in one step from the corresponding amino alcohols and readily available bis-imidates derived from malonate or oxalate [25, 27] or, as described by Masamune et al [28], by amide formation with diethyl malonate and subsequent reaction with dimethyltin dichloride, or by metal-catalyzed condensation of amino alcohols with nitriles [29]. 

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