A sequential addition of silyl cyanide and ketene silyl acetals to esters was achieved by a gallium trihalide catalyst to produce β-cyano-β-siloxy esters. This is the first example of the sequential addition of two different carbon nucleophiles to esters. The employment of lactones provided α,α-disubstituted cyclic ethers with a cyano group and an ester moiety. A variety of esters and lactones are applicable to this reaction system.

The radical coupling of α- or β-iodo phosphorus compounds such as iodo phosphonate, iodo phosphane oxide, and iodo phosphonothioate with butenylindium species, prepared by transmetalation between a (cyclopropylmethyl)stannane and InBr₃, afforded the corresponding cyclopropylmethylated products. The radical reaction was initiated by the radical species generated from butenylindium assisted by a small amount of oxygen. Butenylindium works not only as a cyclopropylmethylating reagent, but also as a radical initiator. For successful coupling, a tin/indium transmetalation was used, where it was important for the tin halide by-product to be inert to the reaction system. In addition, the transmetalation of a (cyclopropylmethyl)stannane and InBr₃ provided the dibutenylindium bromide as a single product, which smoothly coupled with the unstable phosphonyl radical species from the iodo phosphorus compound. A photochemical method (UV irradiation) was also applied and accelerated the coupling reaction. The cyclopropylmethylated phosphonate produced was a good intermediate in the Horner–Wadsworth–Emmons reaction and gave functionalized olefins bearing the cyclopropane moiety.

Boron complexes that contain new tridentate ligands, tris(o-oxyaryl)methanes and -silanes, were prepared. These complexes had a cage-shaped structure around a boron center and showed higher Lewis acidity and catalytic activity than open-shaped boron compounds. The cage-shaped ligands determined the properties of the borates by altering the geometry and were consistently bound to the metal center by chelation. The synthesized compounds were L⋅B(OC₆H₄)₃CH, L⋅B(OC₆H₄)₃SiMe, and its derivatives (L=THF or pyridine as an external ligand). Theoretical calculations suggested that the cage-shaped borates had a large dihedral angle (C_ipso-O-B-O) compared with open-shaped borates. The geometric effect due to the dihedral angle means that compared with open-shaped, the cage-shaped borates have a greater Lewis acidity. The introduction of electron-withdrawing groups on the aryl moieties in the cage-shaped framework increased the Lewis acidity. Substitution of a bridgehead Si for a bridgehead C decreased the Lewis acidity of the boron complexes because the large silicon atom reduces the dihedral angle of C_ipso-O-B-O. The ligand-exchange rates of the para-fluoro-substituted compound B(OC₆H₃F)₃CH and the ortho-phenyl-substituted compound B(OC₆H₃Ph)₃CH were less than that of the unsubstituted borate B(OC₆H₄)₃CH. The ligand-exchange rate of B(OC₆H₄)₃SiMe was much faster than that of B(OC₆H₄)₃CH. A hetero Diels–Alder reaction and Mukaiyama-type aldol reactions were more effectively catalyzed by cage-shaped borates than by the open-shaped borate B(OPh)₃ or by the strong Lewis acid BF₃⋅OEt₂. The cage-shaped borates with the bulky substituents at the ortho-positions selectively catalyzed the reaction with less sterically hindered substrates, while the unsubstituted borate showed no selectivity.

The cover picture shows the species generated in the reductive system of allyl bromide with indium(0) in water. They include monoallylindium(III) dibromide, diallylindium(III) bromide, and allyl(μ-oxido)indium(III). These compounds were characterized on the basis of X-ray analysis. The allylindium compounds showed nucleophilicity towards carbonyl compounds with different reactivities. Details are discussed in the Short Communication by M. Yasuda, A. Baba et al. on p. 5359 ff.

The reductive system of allyl bromide and indium(0) in water generated monoallylindium(III) dibromide and diallylindium(III) bromide. These compounds were characterized by X-ray analysis after complexation with 3,5-dibromopyridine or 4-(dimethylamino)pyridine, respectively. Both isolated complexes showed high nucleophilicity and reacted with benzaldehyde to give the allylation product. The diallylindium(III) bromide was less stable in water than the monoallylindium(III) dibromide. The reaction of the diallylindium(III) with benzhydrol gave a (μ-alkoxido)indium species that showed nucleophilicity. This result suggests that allyl(μ-hydroxido)indium also acted as a nucleophile in an aqueous Barbie-type reaction system.

The InI₃-catalyzed hydroallylation of esters by using hydro- and allysilanes under mild conditions has been accomplished. Many significant groups such as alkenyl, alkynyl, cyano, and nitro ones survive under these conditions. This reaction system provided routes to both homoallylic alcohols and ethers, in which either elimination of the alkoxy moiety or of the carbonyl oxygen atom could be freely selected by changing the substituents on the alkoxy moiety and on the hydrosilane. In addition, the hydroallylation of lactones took place without ring cleavage to produce the desired cyclic ethers in high yields.

The reaction of cinnamyl bromide with indium(0) gave two allylindium species, cinnamylindium dibromide and dicinnamylindium bromide. Either species were isolated after complexation of appropriate pyridine-type Lewis bases. The use of 3,5-dibromopyridine (Br₂py) as a Lewis base gave cinnamylindium dibromide with two Br₂py ligands. Dicinnamylindium bromide was isolated with 4-(dimethylamino)pyridine (Me₂Npy) ligands. In both cases, the indium atom showed a trigonal-bipyramidal coordination sphere with the cinnamyl group(s) and bomine atom(s) in equatorial and the pyridine-type ligands in axial positions. The cinnamylindium bromide transformed to dicinnamylindium bromide with formation of InBr₃ in the presence of Me₂Npy. The dicinnamylindium bromide had a higher reactivity than the monoallyl compound for carbonyl addition.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)