Cycloadditions silver nitrate

In another report, the traditional oxazolidinone auxiliary was attached to the acyl chloride for the [2+2] cycloaddition with an imine. Thus, both Holton s and Palomo s groups reported the reaction of 7.1.12 and 7.1.13 to yield lactam 7.1.14 in a virtually complete stereoselective fashion. The asymmetry at the C-3 position of the lactam was destroyed by hydroxylation or chlorination at this position. Hydrolysis of the auxiliary was achieved with silica gel (Si02) or silver nitrate (AgNOs). Diastereoselective reduction of the key intermediate ketolactam 7.1.15 to give 7.1.16 was then effected with NaBH4 in MeOH at 0°C (241, 242). An alternate approach to chiral /3-lactam uses baker s yeast to reduce racemic ketolactam 7.1.15 (243). The desired isomer 7.1.16 was obtained in up to 80% ee at 50% conversion. 

Silver nitrate is used for the ring-opening of 2-nitrothiophene by amines, and for the asymmetric formal [3+2] cycloaddition reaction of isocyanoacetates to a. unsaturated ketones. Silver nitrate is also used for the separation of homopropar-gylic alcohols from allenic alcohols and for the purification of a rra i, /rans-2,4-hexadienol from its stereoisomers. ... 

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