0000000000535351
AUTHOR
Elmar Bräu
Regioselective Annulation of Alicyclic−Aromatic Dienes with 3-Halo-3-cyclobutene-1,2-diones. Synthesis of Annulated α-Halobenzocyclobutenones1
4-(1-Cycloalken-1-yl)-1,2-dialkoxybenzenes 8, 10, and 11 and 5-(1-cycloalken-1-yl)-1,3-benzodioxoles 12−15 react with the semisquaric halides 5a and 5b in a dehydrative annulation process to give the annulated α-halobenzocyclobutenones 9a,b and 16a,b−21a,b in poor to good yields (20−76%). The reaction failed with alicyclic−aromatic dienes having no or only one alkoxy group in the benzene ring. The dehydrative annulation process could be extended to 4-(3,4-dimethoxyphenyl)-1,2-dihydronaphthalene (24), affording the highly annulated α-chlorobenzocyclobutenone 25 in 50% yield. In the case of 5-(1-cyclobuten-1-yl)-1,3-benzodioxole (22), reaction with the semisquaric halides 5a,b yielded the dic…
On heterocyclic systems containing bismuth(III) 2. Eight-membered heterocycles Cl/Br/I-M(CH2CH2CH2)2X with lewis acidic group 15 atoms M As, Sb, Bi and donor atoms X NR, S: a contribution to the value of the electronegativity of bismuth(III)
Abstract Paths to the ligands (Cl/Br-CH2CH2CH2)2NR/O/S/Se, R Me, Bz, iPr, iBu, to the diGrignard reagents (Cl/BrMg-CH2CH2CH2)2NR/O/S, R Me, Bz, iPr, iBu and to the eight-membered group 15 heterocycles (Cl/Br/I-As/Sb/Bi(CH2CH2CH2)2NR/S, R Me, Bz, iBu are given. 13C-NMR, IR and Raman spectra are discussed; for the compound ClSb(CH2CH2CH2)2NMe the crystal structure analysis is given : the antimony atom is clearly Lewis acidic with ψ-trigonal-bipyramidal coordination and a transannular Sb⋯N interaction of 2.385(2) A. For such a configuration the values of the 13C-NMR chemical shifts of the α-CH2-groups (e.g. Cl-As/Sb/Bi(αCH2CH2CH2)2NMe 34.6, 25.9, 46.6 ppm) display clearly a sequence N > …
Tetraaryl-methane analogues in group 14—V. Distortion of tetrahedral geometryin terms of through-space π–π and π–σ interactions andNMR sagging in terms of π–σcharge transfer
Abstract 44 members of thecompound series Ph4−nMRn (M=Si, Ge, Sn, Pb; R=o-, m-, p-Tol; n=0–4) were synthesized (15 newcompounds). The crystal structures of Ph3Sn (o-Tol) and PhSn (o-Tol)3 were determined and compared to 16 known structures. Subject to the distanced (M–C), an interplay between through-space π–π repulsion and π–σ attraction leads to either elongated or compressed tetrahedral geometry. 29 Si-, 119 Sn- and 207 Pb-NMR chemical shifts were determined in solution and in the solid state.73 Ge chemical shifts were measured only in solution. Anupfield or downfield sagging of the chemical shifts along each series is rationalized in terms of a π–σcharge transfer which is constrained by…
As(III)/Sb(III)/Bi(III)–halide distances and stretching vibrations. An application of the Varshni relationship upon hypervalent group 15 compounds
Abstract A Varshni treatment between stretching frequencies and bond lengths is given for 16 heterocycles of the types Hal–M(SCH 2 CH 2 ) 2 X and Hal–M(CH 2 CH 2 CH 2 ) 2 X (M=As/Sb/Bi, Hal=Cl/Br/I, X=O, S, NR). The intensities of the Raman emissions for the M–Hal bonds increase in the following order: Cl≪Br −1/2 , decrease in the following order: Cl>Br≫I. Practically, the Varshni constants are used to estimate the complementary quantity, stretching frequency or bond length, in 35 cases.
Heterocyclic systems containing tin(IV)—XIII [1]. Possible ceasing or inversion of the structuraltrans influence during the course of a bimolecular nucleophilic attack of a donor group in a series of SnIV rings
Abstract In the series of the heterocycles X[(CH2)3]2SnR2 (16 newly synthesized compounds and two taken from the literature) and in the germanium analog BuiN[(CH2)3]2GeCl2, the donor group X (= NMe, NBz, NBui, NPri, O, S) intramolecularly attacks the Lewis acidic atoms Sn or Ge. Eight structure determinations (and, in addition, 2 taken from the literature) are compared. The nucleophilic attack at Sn is stronger for the ligands R2 =Cl2 than for the more electronegative R2 = (OSiPh3)2. Overall the familiartrans influence holds: simultaneous approach of X and weakening of the ligand R (trans). In three cases of subtly graded donor strength a slight inversion or ceasing is observed: shorter dis…
Heterocyclic systems containing antimony (III) -VIII . Hypervalency by intramolecular 1,5-chelation Sb · · · N in rings RSb [ (CH2) 3] 2NR′ (NR′ = NMe, NBz, NBui) and comparison to analogous compounds of AsIII, BiIII, GeIV and SnIV
Abstract Eleven antimony compounds RSb [ (CH2) 3] 2 NR′ and eight germanium compounds R2Ge [ (CH2) 3] 2 NR′ (some combinations of R = Cl, I, NCS, OSiPh3, Ph, and NR′ = NMe, NBz, NBui) have been synthesized by diGrignard reactions and subsequent treatment with AgSCN, Ph3SiONa or PhLi. The compounds were compared to 14 Sn, 1 As, 5 Sb and 4 Bi analogues taken from the literature. Evidence is provided for 1,5-chelation Sb · · · N via crystal structure determinations (5+1 (lit) Sb compounds) , 13C- and 29Si-NMR chemical shifts, 12;Sb and 12;I Mossbauer data (11 and 3 Sb compounds, respectively) , cyclic voltammetry (9 Sb compounds) and semi-empirical MO calculations on the Extended Huckel level …