Reaction of tetra-n-butylmercaptodiborane with unsaturated compounds

Summary Tetra-n-butylmercaptodiborane reacts with unsaturated compounds at 70–80° in the presence of pyridine to form esters of alkylthioboric acids.     

Structure and stability of the SiH3O2: Radical

A quantum chemical ab initio study of the electronic structure and force constants of the SiH₃O ₂ ^. radical is reported. The minimum on the potential surface corresponds to a C_s symmetry structure (the²A¹¹ term). The Hartree-Fock solution with the minimal energy for this structure does not satisfy the aufbau principle. The calculated enthalpy of SiH₃O ₂ ^. formation from SiH ₃ ^. and O₂(³∑_g ^-) is approximately −30 kcal/mole. Institute of Semiconductor Physics, Siberian Branch, Russian Academy of Sciences. Novosibirsk Institute of Organic Chemistry, Siberian Branch, Russian Academy of Sciences. Institute of Catalysis, Siberian Branch, Russian Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 35, No. 1, pp. 25–30, January–February, 1994. Translated by L. Smolina     

Crystal,molecular, and π-electronic structure of 1,3,2-benzodithiazolium chloride

X-Ray diffraction examination and MNDO calculations have shown that 1,3,2-benzodithiazolium chloride (I) is ionic, with a planar heteroaromatic 10-electron cation. The -MO of the cation (I) is isolobal with the p-MO of benzo-2,1,3-thiadiazole. In the cation of (I), as in the latter compound, the p-AO of nitrogen and sulfur contribute for the most part to -MO of differing symmetry (b₁ and a₂, respectively). This has the consequence that although both nitrogen and sulfur participate in the formation of a single -system in the thiazolium cation of (I), there is virtually no -bonding between them. Generally speaking, the -MO of the (I) cation shows a tendency to localization on separate molecular fragments. The charge on the cation is localized at the SNS group, and the five-membered ring is strongly polarized. These features all reduce the heteroaromaticity of the system.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1683–1688, December, 1990.     

Substituted 1,3,2,4‐benzodithiadiazines: Novel derivatives,by‐products,and intermediates*

The synthesis of the title compounds 1 by 1 : 1 condensation of Ar NSNSiMe₃ 2 with SCl₂ followed by intramolecular ortho‐cyclization of each [Ar NSN S Cl] intermediate is complicated by further reaction of 1 with SCl₂ to give Herz salts 3 . With the 2 :SCl₂ ratio of 2:1, the formation of by‐products 3 is reduced and novel compounds 1 are accessible. With ortho‐I containing starting material 2j , the parent compound 1s is obtained as the result of an unexpected I, not H, substitution. The rate of the 1 + SCl₂ reaction depends upon a substituent's position, and the minor 8‐R isomers 1l,p (R = Br, I) are isolated for the first time from mixtures with the major 6‐R isomers due to reduced reactivity toward SCl₂. The synthesized compounds 1–3 are characterized by multinuclear (including nitrogen) NMR and X‐ray crystallography. According to the X‐ray diffraction data, 1j (6‐Br) and 1k (7‐Br) derivatives are planar, whereas 1i (5‐Br) and 1l (8‐Br) are bent along the S1···N4 line by ∼5° and ∼4°, respectively, and the 1r (7‐OCH₃) derivative is planar in contrast to the known 5‐OCH₃ isomer, which possesses a significantly folded heterocycle. The distortion of the planar geometry of some compounds 1 is interpreted in terms of a pseudo‐Jahn‐Teller effect as the result of π‐highest occupied molecular orbital (HOMO)  σ*‐(LUMO) lowest unoccupied molecular orbital + 1 mixing in a planar conformation. The 2p compound is the first structurally defined Ar–N = S = N–SiMe₃ azathiene. The compound Ar–N = S = N–S–NH‐Ar 6 modeling the aforementioned intermediate has been isolated and structurally characterized. We describe the attempts to synthesize compounds 1 from 2‐aminobenzenethiols and (SN)₄ and from salts 3 and Me₃SiN₃, and we discuss the reaction pathways. © 2001 John Wiley & Sons, Inc. Heteroatom Chem 12:563–576, 2001