Indium(I) Bromide-Mediated Reductive Coupling of α,α-Dichloroketones to 1-Aryl-butane-1,4-diones

Abstract

Indium(I) bromide promotes the reductive coupling of a,a-dichloroketones to the corresponding 1,4-butanediones in moderate to good yields.

Structure and reactivity of derivatives of dihalogenomethyl indium(III) halides, X2InCHX2 (X=Cl, Br, I)

“…These findings indicates that it is possible to modulate the electronic character of the a-halogenoalkyl substituent attached to indium carbenoids of general formula X 2 InCR 1 R 2 X, easily obtained by inserting InX into carbon-halogen bond of dialkyldihalides, R 1 R 2 CX 2 , by the correct choice of the substituents RÕs. Electron withdrawing RÕs groups determine nucleophilic characteristics on the haloalkyl substituent, as indeed we have observed for the compounds derived from dibromoacetonitrile (R 1 = CN, R 2 = H) [16], trichloroacetonitrile (R 1 = CN, R 2 = Cl) [17], and dichloroketones [R 1 = C(O)R, R 2 = H] [18], which easily couple to carbonyl compounds to generate new carbon-carbon bonds. Carbenoids derived from CH 2 X 2 substrates have the halogenomethyl group of considerable electrophilic character to the point to accept electron pair of suitable Lewis bases to generate organoindium ylids of general structure X 3 InCH 2 L, such as we have isolated in previous works [3].…”

Indium(I) bromide-promoted stereoselective preparation of (E)-α,β-unsaturated ketones via sequential intermolecular aldol-type coupling/elimination reactions of α,α-dichloroketones with aldehydes

“…The indium enolate, 3 obtained from the oxidative insertion of InBr into one of the carbon-chlorine bonds of the dichloroketone can be used for several purposes: it couples with a second molecule of the dichloroketone to produce, after reduction with excess of indium monobromide, the corresponding 1,4-butanediones, 7 [5]; alternatively, the enolate condensates with an aldehyde to give the corresponding 2-chloro-3-hydroxy-propan-1-one derivative, 6 [4a]; which can easily be converted into the trans-epoxyde 8 by treatment with a convenient base (Scheme 3) [4a]. Now, we have extended this sequence of reactions to produce the (E)-a,b-unsaturated ketones 2, through an aldol coupling followed by an elimination reaction.…”

Dihalogen–halogenomethyl complexes of indium(III) X2InCH2X (X=Br, I): Simultaneous coordination of soft and hard ligands

“…Similarly, oxidative insertions of InX into the carbon-halogen bonds of organyl dihalides, RR 1 CX 2 (R = R 1 = H, X = Br, I [3,4]; R = H, R 1 = CN, X = Br [5]; R = H, R 1 = PhCO, X = Cl [6,7]) and trihalides, RCX 3 (R = H, X = Cl, Br, I [8][9][10]; R = CN, X = Cl [11]) lead to the corresponding halogenoalkyl, X 2 InC-RR 1 X and the dihalogenoalkyl, X 2 InCRX 2 compounds of indium(III). While some of these compounds contain nucleophilic alkyl substituents capable of coupling to electrophiles [5][6][7]10,11], the methylene dihalide derivatives have been used mainly as models for coordination chemistry studies.…”

“…Similarly, oxidative insertions of InX into the carbon-halogen bonds of organyl dihalides, RR 1 CX 2 (R = R 1 = H, X = Br, I [3,4]; R = H, R 1 = CN, X = Br [5]; R = H, R 1 = PhCO, X = Cl [6,7]) and trihalides, RCX 3 (R = H, X = Cl, Br, I [8][9][10]; R = CN, X = Cl [11]) lead to the corresponding halogenoalkyl, X 2 InC-RR 1 X and the dihalogenoalkyl, X 2 InCRX 2 compounds of indium(III). While some of these compounds contain nucleophilic alkyl substituents capable of coupling to electrophiles [5][6][7]10,11], the methylene dihalide derivatives have been used mainly as models for coordination chemistry studies. Independently, we have determined that ligands with the hard donor atom oxygen, L H , such as ethers, dimethylsulfoxide and triphenylphosphine oxide coordinate to the metallic center of the Br 2 In(L H ) n CH 2 Br complex [12], while bases with soft donor atoms, L S , displace the bromine atom of the bromomethyl substituent to form corresponding ylides of InBr 3 of general structure Br 3 InCH 2 L S [13][14][15][16][17].…”