Cerium trichloride

Addition of 2,6-dimethoxypyrimidine-4-cerium chloride 371 to the chiral lactone 370 occurred without racemization of the chiral center, and the product 372 was subsequently used in a successful total synthesis of (—)-7-epicylindro-spermopsin <2002JA4950, 2005JOC1963>. The cerium reagent was prepared situ from 4-bromo-2,6-dimeth-oxypyrimidine by sequential addition of butyllithium and cerium trichloride. Addition of the same dimethoxypyrimidine-4-cerium derivative to a chiral lactam has also been reported <1999J(P1)1193>. 

Organocerium derivatives posses low basicity. 5-Pyrimidylcerium dichlorides (e.g. 881) are available by low-temperature metal-metal exchange using cerium trichloride and 5-lithiated pyrimidines (e.g. 880, R = SMe, R = H). The 5-pyrimidinylcerium dichloride was superior to its 5-lithio analogue in reactions with aldehydes and ketones, especially in reactions with enolizable aldehydes and ketones (89ACS816). 

Reduction to diol 16 was achieved with a variation of the method of Luchc 5 involving sodium borohydnde and cerium trichloride. The initial product is cyclic hemiacetai 51, which is opened and reduced via intermediate 52 ultimately to diol 16. 

Under appropriate experimental conditions, hydrogen telluride, phenyl tellurol, and sodium hydrogen telluride perform the selective reduction of double bonds of a,/3-unsaturated carbonyl systems.89 90 This reaction with a,j3-unsaturated ketones complements the cerium trichloride/sodium borohydride method, which reduces the carbonyl group, keeping the carbon-carbon double bond intact92 (Scheme 18). 

Ce [60,61] See Section 6.1. Ultrasound irradiation is beneficial for the reaction of organolithium compounds with cerium trichloride, and would presumably be so for organomagnesium compounds [62]... 

Sodium bis(2-methoxyethoxy)aluminum) hydride. Sodium borohydride-Cerium trichloride. Sodium cyanoborohydride. Sodium dithionite. Sodium hydroxy-... 

SYNS CERIUM(III) CHLORIDE CERIUM TRICHLORIDE CEROUS CHLORIDE... 

The use of cerium trichloride for the Peterson alkenation has been q)plied by Ueda and cowoikers for nucleoside synthesis (Scheme S2). The anion was generated with LDA/cerium trichloride and condensed with the aldehyde (375). The product was treated with KH in THF and the pyrimidopyridine (377) isolated in S0% yield. 

Luche, J. L., Rodriguez-Hahn, L., Crabbe, P. Reduction of natural enones in the presence of cerium trichloride. J. Chem. Soc., Chem. Commun. 1978, 601-602. 

Sodium Borohydride/Cerium Trichloride (Luche Reduction)... 

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