Oppolzer, camphorsultam auxiliary

As one of the pioneering works on asymmetric synthesis, Evans and coworkers reported diastereoselective Diels-Alder reaction of acryloyl oxazolidinones mediated by Et2AlCl [140]. Intramolecular version of this cycloaddition was also reported, in which interesting stereochemical difference depending on substituents at oxazo-lidinone ring was found. As an another excellent example, Oppolzer and coworkers reported diastereoselective Diels-Alder reaction of chiral dienophiles equipped with camphorsultam auxiliary [141]. Recently, these diastereoselective reactions were applied to enantioselective synthesis of ceralure Bl, known as Mediterranean fruit fly attr actant (Scheme 6.118) [142]. 

In addition to the synthesis of enantiomerically pure (camphorylsulfonyl)oxaziridine7 and its derivatives,8 the (camphorsulfonyl)imine has been used in the preparation of (-)-2,10-camphorsultam (Oppolzers auxiliary),6-9 (+)-(3-oxocamphorysulfonyl)oxaziridine10 and the N-fluoro-2,10-camphorsultam, an enantioselective fluorinating reagent.11... 

Smith exploited a Lewis-acid-mediated asymmetric Diels-Alder reaction34 between 1,3-butadiene and the Oppolzer acryloyl camphorsultam 78 to set the remote C(29) stereocentre in phenylsulfone 57 (Scheme 17.17). This tactic procured acid 8 in 93% enantiomeric excess (ee), after base-promoted hydrolysis of the chiral auxiliary. Utilising a procedure published by Martin and co-workers,35 Smith iodolactonised acid 8, and... 

Oppolzer s chiral auxiliary,6 (-)-2,10-camphorsultam, is useful in the asymmetric Diels-Aider reaction,3.4 and for the preparation of enantiomerically pure p-substituted carboxylic acids7 and diols,8 in the stereoselective synthesis of A2-isoxazolines,9 and in the preparation of N-fluoro (-)-2,10-camphorsultam, an enantioselective fluorinating reagent.10... 

The chiral auxiliary approach. Poncas group has worked with chiral sulfur moieties like 10-methylthioisoborneol, Oppolzer s camphorsultam or chiral oxazolidinones which gave excellent results in stereo control and yields [95-100]. Recently they have reported that chiral alkynylthiols like 46 exhibit excellent diastereoselectivities in both inter- and intramolecular PKR, and have used this approach for the synthesis of 47, an intermediate in the synthesis of (+)-15-nor-pentelenene (48) (Scheme 15) [101,102]. 

Chiral auxiliary approaches have been examined for the production of enantioenriched products through [2,31-rearrangements. For example, Sweeney and coworkers treated N,N-dimethylammonium salts 186 with sodium hydride to generate ammonium ylides bearing Oppolzer s camphorsultam, which underwent diastereoselective [2,31-Stevens rearrangements to enantioenriched products 187 [Scheme 1S.44. Eq. Oppolzer s camphorsultam was also compatible with our group s palladium-catalyzed tandem allylic amination/[2,31-Stevens rearrangement of tertiary amines [Scheme 1S.44. Eq. 2) ... 

The related phthallmldyl dlazoacetate (25) has yielded series of dlazoacetamldes bearing Oppolzer s camphorsultam chiral auxiliary (eq 17). ... 

Of great interest is the use of Oppolzer s camphorsultam as chiral auxiliary in a zinc-mediated allylation of oximes in the Luche conditions ... 

Oppolzer s acylated camphorsultams (147, Equation 12) remain a classic among chiral auxiliaries for asymmetric synthesis and have been successfully applied in a variety of mechanistically distinct chemical transformations [88, 91]. The corresponding enolates can readily be prepared with a variety of strong bases and have been shown to undergo diastereoselective alkylation with a range of activated and non-activated electrophilic reagents. An illustrative example is the formation of 149 in dr >99 1 [91]. The sense... 

The use of amides and imides as chiral auxiliaries in [4 + 2]-cycloadditions has been the subject of numerous investigations. Oppolzer reported the use of camphorsultam 112 in asymmetric Diels-Alder reactions [26, 67. 68], The camphor sultam is readily available in both enantiomeric forms from cam-phorsulfonyl chloride. Acrylate 113 was found to react with cyclopentadiene in the presence of EtAlCl2 to give 115 with high selectivity (endo/exo = 99.5 0.5, dr = 97.5 2.5, Equation 10) [67]. Oppolzer also reported that triene 116 participated in an intramolecular Diels-Alder cycloaddition reaction to afford endo product 117 in 71 % yield and 96.5 3.5 dr (Scheme 17.19) [69]. This bicyclic product was subsequently converted into the pyridine alkaloid (-)-pulo upone (118). 

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