Lead-Mediated Highly Diastereoselective Allylation of Aldehydes with Cyclic Allylic Halides

Abstract

Lead was found to efficiently mediate the allylation reactions of carbonyl compounds with cyclic allylic halides in the presence of stoichiometric amounts of lithium chloride and a catalytic amount of GaCl3 (20 mol %), leading to the desired homoallylic alcohols in modest to high yields with excellent diastereocontrol (>99:1 syn/anti) and good functional group tolerance. In contrast, the use of either 2-pyridinecarboxaldehyde as the carbonyl substrate or (E)-cinnamyl bromide as the allylating agent produced the corresponding product with reversed diastereoselectivity (>99:1 anti/syn).

Nickel-Catalysed Allylboration of Aldehydes

“…The data are consistent with the literature. 37 R f = 0.16 (10% Et 2 O/n-hexane). 1-(4-Chlorophenyl)-pent-3-en-1-ol (5g) The title compound was prepared according to general procedure 1 from 4-chlorobenzaldehyde (45.2 mg, 0.321 mmol) and boronic ester 4g (72.5 mg, 0.398 mmol).…”

Iron(0)-Mediated Reformatsky Reaction for the Synthesis of β-Hydroxyl Carbonyl Compounds

“…As expected, preliminary studies showed that almost no desired product 3a was obtained when the reaction was performed in the absence of any catalyst (entry 1). When various metallic salts (20 mol %) were employed as the reaction catalyst (entries 2–15), such as InCl 3 , , GaCl 3 , PbCl 2 , , CrCl 3 , FeCl 3 , LiI, and CuI, which were demonstrated to be efficient catalysts for catalyzing some other organic reactions, the reactions proceeded with different performances to afford the corresponding β-hydroxyl ester 3a in poor yields, ranging between 2% and 39%. It was not until molecular iodine was introduced as a reaction catalyst that the yield of product 3a was remarkably improved to 90% (88% isolated yield; entry 16).…”