T.H. Chan

Organometallic reactions in aqueous media with indium

Allylation reactions of aldehydes and ketones occurred smoothly with indium metal in aqueous media. Compared to similar reactions with zinc and tin, the reaction with indium proceeds without the need of any promoter. The reaction can be extended to the synthesis of 2-methylene-γ-lactone 6 via the condensation of carbonyl compounds with 2-bromomethylacrylate 4.

Lewis acid promoted condensation of carbonyl compounds with alkoxyallylsilanes synthesis of substituted tetrahydropyrans

Abstract The condensation of alkoxyallylsilanes with carbonyl compounds under Lewis acid conditions gave all cis -4-chloro-2,6-disubstituted-tetrahydropyrans. The reaction was found to proceed through a mixed silyl acetal intermediate.

A rapid, mild and acid-free procedure for the preparation of acyl chlorides including formyl chloride

Abstract Carboxylic acids are converted by hexachloroacetone and triphenylphosphine at −78 °C in methylene chloride to the corresponding acyl chlorides. Formic acid can be used to generate formyl chloride at −78 °C in order to perform formylation under very mild conditions.

Regioselection in the alkylation of trimethylsilylallyl anion-stereoselective synthesis of disubstituted alkenes

Abstract The regioselection in the alkylation of trimethylsilylallyl anion can be controlled by the use of Schlossers base to give predominately γ-product with trans-geometry at the double bond. Application of this approach to the synthesis of Z-9-tricosene and the Gypsy moth sex pheromone is demonstrated.

Conversion of primary amides into active acylating agents via acylpyrroles.

Several primary amides were converted to N-acylpyrroles on reaction with 1,4-dichloro-1,4-dimethoxybutane (1) and Amberlyst A-21 resin. The acylpyrroles act as active acylating agents.

Stereoselection in the condensation between ethyl propionate and aldehydes

Abstract Ethyl propionate can be converted stereoselectively into geometrical isomers of O-ethyl-O-trimethylsilylmethylketene acetal ( 5 ). The E-isomer of 5 condenses with aldehydes by titanium tetrachloride to give stereoselectively the threo isomers of ethyl 2-methyl-3-hydroxy carboxylates.

Regioselective alkylation of 1-silyl-2-methylallyl carbanions

Abstract Regioselective alkylations of 1-silyl-2-methylallyl carbanions were achieved by changing the substituents on silicon. γ-Alkylation was favoured by dialkylamino group on silicon, whereas α-alkylation was favoured by an alkoxy substituent on silicon.

Reactions of enol silyl ethers with N-halosuccinimide - a stepwise process

Abstract The N-chlorosuccinimide (NSC) reaction of a number of cyclic and acyclic trimethylsilyl enol ethers was investigated. Based on product analyses, the mechanism of the reaction is postulated to involve a step-wise process.

Rearrangement of α-acyloxyacetates into 2-hydroxy-3-ketoesters

Abstract α-Acyloxyacetates rearrange under LDA conditions to give 2-hydroxy-3-ketoesters. The corresponding trimethylsilyl- or acetyl derivatives can be obtained by quenching the reaction mixture with Me 3 SiCl or Ac 2 O.

Silver-assisted reactions of organotin oxides. A mild, neutral and anhydrous one-step conversion of primary organic halides to alcohols

Abstract Bis(tributyltin)oxide acts as a mild and neutral oxygen transfer agent in converting primary organic iodides and bromides into alcohols in good to excellent yields. The less reactive chlorides can be converted into alcohols when they are first transformed into bromides or iodides using the Finkelstein reaction. Silver salts are required for this one step conversion.