Alkene protection

Phthalimidoaziridines can be cleaved by hydrazinolysis to give 1-aminoaziridines, which decompose slowly at room temperature, and rapidly above 48 C, regenerating the starting alkene with stereochemistry intact. There would appear to be some unexploited potential for phthalimidoaziridines to be used for alkene protection. Phth imidoaziridines are stable to reflux in chlorobenzene (132 C) for 24 h. A/-Aminoaziridines can be acylated to yield )V-acylaminoaziridines of varying thermal stability (34 ti/2 = IS min at 37 C) is a ready thermal source of benzamidonitrene from which new aziridines can... 

Kna 7 has used the oxyanion-accelerated rDA reaction to advantage in the synthesis of conduritol A. The masked dienol used was 9-[(benzyloxy)methoxy]anthracene (81), which upon reaction with benzo-quinone (82) gave the protected adduct (83) (equation 38). Further transformations yielded (84), which upon treatment with potassium hydride caused rDA fragmentation to occur at 35 °C. Two subsequent steps produced conduritol A (86a), a naturally occurring cyclitol, in 39% overall yield from (82). The room-temperature DA activity of anthranol reported by Rickbom, coupled with the observed low-temperature rDA reactivity of its adducts, makes anthranol a highly useful alkene protecting group via a DA/iDA sequence. 

Electrophilic addition to alkenes ch19 Reduction of benzene rings Reagents for oxidation of alcohols Reagents for oxidation of alkenes Protection of aldehydes, ketones, alcohols, and amines Synthesis of peptides Cycloadditions ch34... 

Type IV 1,1-Disubstituted alkenes, disubstituted a,p-unsaturated carbonyls, tertiary aUylic carbon-containing alkenes, perfluoroalkyl alkenes, protected tertiary aUylamines... 

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