Tsunehisa Hirashita

Regioselective allylation and alkylation of electron-deficient alkenes with organogallium and organoindium reagents

Abstract Triorganogallium and -indium reagents reacted with α,β-unsaturated nitrile and carbonyl compounds to give 1,4-addition products regioselectively. The reaction of allylgallium and allylindium sesquihalides with α,β-unsaturated carbonyl compounds proceeded in a 1,2-addition mode, whereas a 1,4-addition took place with α,β-unsaturated nitriles.

Allylindation of Cyclopropenes in Organic and Aqueous Media: Switching the Regio- and Stereoselectivity Based on the Chelation with a Hydroxyl Group and the Crystal Structure of the Cyclopropylindium Product

Hydroxy-bearing cyclopropenes react with allylindium reagents to undergo clean allylindation both in organic and aqueous media, in which the chelation of the hydroxyl group to indium plays the central role. The regio- and stereoselectivity have been regulated both by the location of the hydroxyl group in the molecules and the reaction solvents. In particular, the allylindation in water shows marked differences from that in organic solvents; the regio- and stereoselectivity have totally been reversed compared with those in organic solvents. Unusually stable cyclopropyl-indium compounds have been isolated from the reaction of 1-(omega-hydroxyalkyl)cyclopropenes and the structure has fully been established by X-ray crystallography.

Stereodivergent allylindation of cyclopropenes. Remarkable stereodirection and acceleration by neighbouring carboxyl and hydroxyl groups

Abstract Stereodivergent allylindation of cyclopropene derivatives has been realised regio- and stereoselectively. The coupling occurs exclusively at the γ-carbon of allylic indium reagents and the more substituted carbon of the cyclopropene double bond. The carboxyl and hydroxymethyl groups on the cyclopropene C 3 -carbon exert significant effects in cis -direction and acceleration of the allylindation based on the intramolecular chelation, whereas the ester group directs a trans -addition owing to the steric interaction with incoming allylindium reagents.

Reaction of α-halo organoindium reagents with carbonyl compounds and electron-deficient alkenes

Abstract A variety of α-halo organoindium reagents were prepared in situ from the reaction of gem -dihalo compounds with indium metal, and their reactions with carbonyl compounds and electron-deficient alkenes were examined. The reactions of simple 1,1-diiodoalkanes with indium metal gave no defined products but benzal iodide gave stilbene in a moderate yield. α-Halo organoindium reagents drived from α,α-dibromo carbonyl compounds gave oxiranes and cyclopropanes upon the reactions with aldehydes and alkenes, respectively. 3,3-Dichloropropenes reacted with aldehydes in the presence of indium metal to give the corresponding chlorohydrins and/or homoallylalcohols, depending on the structures of both the dichloropropenes and aldehydes employed.

Control of diastereoselectivity in the crotylation and cinnamylation of aldehydes by the selection of ligands on allylic indium reagents

Diastereoselective couplings of salicylaldehyde, anisaldehyde and 2-pyridylaldehyde with crotyl- and cinnamylindium reagents were studied. The syl/anti selectivity was found to depend largely on the ligands on the indium atom of the allylic indium reagents. A syn-selective cinnamylation of salicylaldehyde was realized by the combination of cinnamyl acetate and indium(I) iodide, whereas an anti-selective coupling with salicylaldehyde was achieved by the indium trichloride/aluminium-mediated cinnamylation.

Stereoselective synthesis of halocyclopropanes via halogenation of cyclopropylindium reagents

A stereoselective synthesis of halocyclopropanes has been achieved via halogenation of the cyclopropylindium reagents prepared from allylindation of cyclopropenes.

INDIUM-MEDIATED REACTION OF 1,3-DICHLORO- AND 1,3-DIBROMOPROPENES WITH CARBONYL COMPOUNDS. GENERATION OF NOVEL 3,3-DIINDIOPROPENE

Indium-mediated reaction of 1,3-dichloropropene with aldehyde gave syn-chlorohydrin predominantly. A similar reaction of 1,3-dibromopropene gave viayloxirane and homoallyl alcohol; the former is formed from γ-bromoallylindium via the corresponding bromohydrin, and the latter is considered to be derived from a unique allylic diindium reagent, 3,3-diindiopropene.

CHELATION-CONTROLLED REGIO- AND STEREOSELECTIVE ALLYLINDATION OF NORBORNENOLS

The first allylindation of norbornenol derivatives has been realised highly regio- and stereoselectively. The reactions of allylindium sesquiiodide with syn-bicyclo[2.2.1]hept-2-en-7-ol and endo-bicyclo[2.2.1]hept-5-en-2-ol gave allylated products together with iodinated and oxygenated compounds. The product distribution could be controlled by changing the reaction solvent. In these reactions, the regio- and stereochemistry of the addition of the allylindium reagent is highly regulated via the chelation with the neighbouring hydroxyl group.

High γ-selectivity in the coupling of penta-2,4-dienyl- and pent-2-en-4-ynylindium reagents with aldehydes

Abstract A variety of penta-2,4-dienyl- and pent-2-en-4-ynylindium reagents have been prepared in situ from the reaction of the corresponding allylic bromides with indium metal, and their reactions with carbonyl compounds have been examined. The reaction with aldehydes gives the corresponding homoallyl alcohols in high yields. The coupling occurs regioselectively at the γ-position of these indium reagents. No α- and ϵ-coupling products are formed.

A new synthesis of pyrroles by the condensation of cyclopropenes and nitriles mediated by gallium(III) and indium(III) salts

Gallium(III) and indium(III) halides were found to mediate the condensation of cyclopropenes and nitriles to give pyrrole derivatives in moderate yields. When excess nitrile was present, diazepine was also formed.