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A novel tricyclic bispidine ligand is prepared and successfully applied as a chiral ligand in Cu-catalyzed asymmetric Henry reactions.

Sulfur diimides R 1 (NSN)R 2 (1) with different substituents R 1 and/or R 2 or with functional groups react with hexachlorodisilane (2) or octachlorotrisilane (3) to give the corresponding diaminosulfanes (4, 5) in quantitative yield. The formation of cyclic intermediates prior to the redox process is discussed. The products have been characterized by 1 H, 13 C, 15 N and 29 Si NMR in solution as well as by 15 N and 29 Si CP/MAS NMR in the solid state (4a, 4f)

Tris[ethynyl(dimethyl)silyl]methane 1 and tris[trimethylstannylethynyl(dimethyl)silyl]methane 2 react with triethylborane 3via a threefold 1,1-ethylboration to give the new bicylic compounds 4 and 5 in good yields; the molecular structure of 5 was determined by a single crystal X-ray analysis.

Trimethyltin alkoxides (2) react stereoselectively with 3-diethylboryl-4-ethyl-1,1-dimethylstannole (1) via addition of the Me3Sn group to C(2) to the C(2) = C(3) bond and a 1,2 shift of an ethyl group from boron to C(3) to give the 2-stannolenes 3. The molecular structure of 3f' [R = (S)-2-Bu] was determined by single-crystal X-ray analysis, confirming the cis positions of the Et(RO)B and the Me3Sn group. These 2-stannolenes 3 undergo, upon heating to ca. 80°C, facile rearrangement by irreversible allylic migration of the Et(RO)B group to the 3-stannolenes 4 in which the cis positions of the boryl and the stannyl group are retained. All 2-stannolenes (in contrast to the 3-stannolenes) are readily deprotoborylated to give the 3-stannolene 5. The structures of 3, 4, and 5 follow conclusively from 1H-, 11B-, 13C-, and 119Sn-NMR spectra. The negative sign of the geminal coupling constants 2J(SnSn) was determined in the case of 3, 4, and 5 by 2D 119Sn/1H heteronuclear shift correlations.

1,2-Di-1-propynyl-tetramethyldisilan (1) reacts with triorganoboranes R3B [R = Et (2a), CH2Ph (2c), 2-thienyl (2d)], 9-ethyl-9-borabicyclo[3.3.1]nonane (3), and diethyl(N-pyrrolyl)borane (4) by twofold 1,1-organoboration to give selectively the respective organo-substituted 1,2-dihydro-1,2,5-disilaborepines 5a-d,6, and 7 in high yields. The compounds 5–7 were characterized by 1H-, 11B-, 13C-, and 29Si-NMR spectroscopy in solution. The molecular structures of the distance 1 and of the heterocycle 5c were determined by X-ray structure analysis.

Bicyclic B-alky-N-pyrrolylboranes (1–3) react with alkyl lithium or alkyl Grignard reagents to give the corresponding borates 5 which, in most cases can be protonated to the intramolecular 2 H-pyrrole-borane adducts 4. The molecular structure of 4d was determined by X-Ray structural analysis. The adducts 4 can be deprotonated to the borates 5. Cleavage of the B-N bond in 1a by EtOH to give 7a is reversible, and 1e react with CF3SO3H by protonation of the pyrrole ring. The 2H-pyrrole-borane adducts 4a,d react with CF3SO3H by cleavage of the B-N bond to give trialkylboranes as the 2H-pyrrolium salts 8a,d. Cyclopentadiene reacts with the 2H-pyrrole borane adduct 4d selectively by [4 + 2]cycloaddition to give 10 with endo-configuration. The boranes 1a and 2a react stereoselectively with mono-1-alkynyltin compounds in a 1:1 stoichiometry by an 1,1-organoboration to give the organometallic substituted alkenes 11–13, in which the six-membered ring present in 1a and 2a is retained. In contrast, 3a reacts under the same conditions exclusively by ring enlargement and in a 1:2 stoichiometry. The product from the reaction of 3a with two equivalents of trimethyl(l-propynyl)tin is the 1,3-butadiene derivative 14 which rearranges selectively to its isomer 15 by changing the configuration at both double bonds. The reaction of 3a with two equivalents of bis(trimethylstannyl)ethyne leads selectively to the organometallic substituted allene 16, the result of an irreversible allylic rearrangement of a 1,3-butadiene derivative analogous to 14 or 15. AH products were characterized by 1H, 11B, 13C, 14N and 119Sn NMR spectroscopy.

The brown crystals of [NEt4]2[Se3Br8(Se2Br2)] (1) were obtained when selenium and bromine reacted in the solution of acetonitrile in the presence of tetraethylammonium bromide. The crystal structure of 1 has been determined by the X-ray methods and refined to R = 0.0308 for 10433 reflections. The crystals are monoclinic, space group P21 with Z = 2 and a = 12.0393(3) A, b = 11.8746(3) A, c = 13.1946(3) A, β = 96.561(1)° (123 K). In the solid state structure the anion of 1 is built up of Se3Br8 unit which consists of a triangular arrangement of three planar SeBr4 units sharing a common edge through two μ3-bridging Br atoms, and one Se2Br2 molecule which is linked to one of μ3-bridging Br atoms. The three SeII atoms form a triangle which is almost perpendicular to the planes given by three SeBr4 moieties. The contact between the μ3Br and the SeI atom of the Se2Br2 molecule is 3.1711(8) A and can be interpreted as a bond of the donor-acceptor type with the μ3Br as donor and the Se2Br2 molecule as acceptor. The terminal SeII-Br and μ3Br-SeII bond lengths are in the ranges 2.3537(7)–2.4737(7) A and 2.7628(7)–3.1701(7) A, respectively. The bond lengths in coordinated Se2Br2 molecule are: SeI-SeI = 2.2636(9) A, SeI-Br = 2.3387(11) and 2.3936(8) A.

A survey is presented on various reactions of Cp * V(CO) 4 , including CO ligand substitution and/or oxidative decarbonylation, to give complexes in which the formal oxidation state of vanadium may vary from 0 to V. Diamagnetic Cp * V complexes can be rapidly and conveniently characterized by 51 V NMR spectroscopy.

Selective C- over O-/N-acylation of acyclic, carbocyclic and heterocyclic carbonyl compounds bearing active α-CH groups is described. β-Ketoesters give the corresponding α-acylylidic derivatives in good yields. Likewise, tetronic acids and 4-hydroxycoumarins furnish the respective 3-acylylidic derivatives, and pyrazol-5-ones exclusively yield the corresponding 4-acylylidic compounds despite the possibility of tautomerism. X-Ray single crystal structure and NMR analyses of the product tricarbonyl ylides are presented and structure–reactivity interdependencies are discussed. As a rule, compounds with wide-spread conjugation of the π-system like 9/13 do not readily undergo Wittig olefination. Acylylides 11 with separated β-keto moieties react normally.