Synthesis of 2H-Chromenes via Hydrazine-Catalyzed Ring-Closing Carbonyl-Olefin Metathesis

The catalytic ring-closing carbonyl-olefin metathesis (RCCOM) of <i>O</i>-allylsalicylaldehydes to form 2<i>H</i>-chromenes is described. The method utilizes a [2.2.1]-bicyclic hydrazine catalyst and operates via a [3+2]/retro-[3+2] metathesis manifold. The nature of the allyl substitution pattern was found to be crucial, with sterically demanding groups such as adamantylidene or diethylidene offering optimal outcomes. A survey of substrate scope is shown along with a discussion of mechanism supported by DFT calculations. Steric pressure arising from syn-pentane minimization of the diethylidene moiety is proposed to facilitate cycloreversion.

Synthesis of 2H-Chromenes via Hydrazine-Catalyzed Ring-Closing Carbonyl-Olefin Metathesis

The catalytic ring-closing carbonyl-olefin metathesis (RCCOM) of <i>O</i>-allylsalicylaldehydes to form 2<i>H</i>-chromenes is described. The method utilizes a [2.2.1]-bicyclic hydrazine catalyst and operates via a [3+2]/retro-[3+2] metathesis manifold. The nature of the allyl substitution pattern was found to be crucial, with sterically demanding groups such as adamantylidene or diethylidene offering optimal outcomes. A survey of substrate scope is shown along with a discussion of mechanism supported by DFT calculations. Steric pressure arising from syn-pentane minimization of the diethylidene moiety is proposed to facilitate cycloreversion.

Reaction of alcohols and silyl ethers in the presence of an indium/silicon-based catalyst system: Deoxygenation and allyl substitution

An In(III)/Si catalyst system effects the direct allyl substitution of alcohols and silyl ethers under mild conditions. A deoxygenation of alcohols is also promoted by InCl3 catalyst. This method requires no pretreatment or protection of hydroxy groups or deprotection of siloxy groups. The completion of the catalytic allylation depends on the low oxophilicity and high halophilicity of In(III) halide species, and other representative Lewis acids such as AlCl3 and BF3 have no catalytic activity for the allylations. The oxophilicity and halophilicity are also demonstrated by NMR studies.

The stereochemistry of organometallic compounds. XVII. Reactions of π-allylpalladium compounds with acetylacetone

Reactions of π-allylpalladium compounds with sodium acetylacetonate, sodium malononitrile, and sodium ethylacetoacetate in dimethyl sulfoxide solution give diallyl substitution products. Reaction of the acetylacetonate complexes with carbon monoxide in benzene give mono- allyl substitution products. Application of these reactions to the π- allyl complexes from 1-acetyl-4-t-butylcyclohex-1-ene and from 3-oxo 4- ene steroids in an attempt to examine the stereochemistry of ligand transfer gave no substitution products.