Camphor imines esters

One problem in the anti-selective Michael additions of A-metalated azomethine ylides is ready epimerization after the stereoselective carbon-carbon bond formation. The use of the camphor imines of ot-amino esters should work effectively because camphor is a readily available bulky chiral ketone. With the camphor auxiliary, high asymmetric induction as well as complete inhibition of the undesired epimerization is expected. The lithium enolates derived from the camphor imines of ot-amino esters have been used by McIntosh s group for asymmetric alkylations (106-109). Their Michael additions to some a, p-unsaturated carbonyl compounds have now been examined, but no diastereoselectivity has been observed (108). It is also known that the A-pinanylidene-substituted a-amino esters function as excellent Michael donors in asymmetric Michael additions (110). Lithiation of the camphor... 

Chiral auxiliaries may be applied to a-amino acid esters by forming imine derivatives. Enolates from 2-hydroxy-3-pinanone glycinate esters have been alkylated to produce mono- and di-substituted o-amino acids in good optical yields after hydrolysis. Recently, McIntosh et al reported the results of alkylations of the enolate (139) derived from the (+)-camphor imine of r-butyl glycinate with a variety of... 

Camphor imines prepared from (+ )-camphor and ( > or (R)-a-phenylethylamine have been reduced with sodium borohydride to yield exclusively the endo- and coco-product, respectively59. An imine prepared from ketopinic acid ethyl ester and benzylamine has been reduced with excess diisobutylaluminum hydride to give the e.w-amino alcohol exclusively61. 

R,4R)-N-(tert-bMoxy-carbonylmethyl)-camphor imine (—)-camphor oxime 7 (-)- Ar-[(1 R,4if)-2-bornylidene]-glycine terr-butyl ester D.l.5.2.4. 5 F... 

Addition of the imine of camphor and glycine, as the Michael donor, to a,/i-unsaturated esters yields, after removal of the auxiliary, anP -(22 )-3-substituted glutamates208. 

Nitrosolysis of camphor ethyl acetal with ethanolic ethyl nitrite in sulphur dioxide yields the orthoester oxime (205) which is rapidly dehydrated by excess acetal to the orthoester nitrile which then reacts with sulphur dioxide to form the ester nitrile and diethyl sulphite.Further papers in this section include the full paper on ozonolysis of silyl ethers (Vol. 5, p. 33), another synthesis of camphor-enol trimethylsilyl ether (cf. Vol. 6, p. 41)/°° the conversion of camphor oxime with Grignard reagents into the corresponding imine with no aziridine formation/° the preparation of (206) by treating bornylene with trichloroacetyl isocyanate/ the oxidation of thiocam-phor to the 5-oxide and alkylation in the presence of thallium(i) ethoxide to a/S-unsaturated sulphoxides/ and the free-radical C-3 alkylation of camphor with alkenes. " ... 

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