Selective Consecutive Insertion of Alkynes into the B–Se Bonds of 1,3,2‐Diselenaborolane Derivatives: Synthesis and Molecular Structures of Nine‐Membered Rings

Abstract

Various alkynes have been inserted selectively and stepwise into the B-Se bond(s) of 1,3,2-diselenaboracyclopentanes {as the 4,5-[1,2-dicarba-closo-dodecaborano(12)] derivatives}. The B-phenyl derivative was much less reactive than the Bhalogeno derivatives. The proposed structures were confirmed in solution by multinuclear NMR studies ( 1 H, 11 B, 13 C and 77 Se NMR), also supported by DFT calculations of the gas-phase molecular geometries and NMR parameters [B3LYP/6-311+G(d,p) level of theory]. Isotope-induced nu-Eur. J. Inorg. Chem. 2012, 3909-3922 [a] Coupling constants n J( 77 Se, 13 C) are given in brackets [Ϯ0.5 Hz], 1 Δ 10/11 B( 13 C(2,3) carb ) Ϯ 0.5 ppb are given in braces {Ϯ0.5 Hz}, isotopeinduced chemical shifts 1 Δ are given in ppb, and the negative sign denotes a shift of the NMR signal of the heavy isotopomer to a lower frequency; n.o. = not observed; [br.] denotes broad 13 C or 77 Se resonances of boron-bonded carbon atoms. [b] Other δ 13 C data: 128.7 (C m ), 132.7 (C p ), 133.8 (C o ), n.o. (C i ) (for Ph).www.eurjic.org 3910 pected, 2e was inert towards all alkynes studied, most likely for electronic and steric reasons.Two different terminal alkynes were used for reactions with 2a (Scheme 3). In contrast to the reaction of phenylethyne, which afforded a complex mixture not analysed as yet, tert-butylethyne gave meaningful results in the first Insertion of Alkynes into B-Se Bonds of Diselenaborolanes Scheme 4. Reversible reaction of 1,3,2-diselenaborolane 2d with hex-3-yne.

Recent Advances in Boron‐Substituted 1,3‐Dienes Chemistry: Synthesis and Application

“…1,1‐Carboboration of dialkynyl‐ and tetraalkynylsilanes opens a convenient route to cyclic silanes such as siloles 60 or bisiloles 56 . The reaction with alkynyl(diorgano)tin compounds (R 1 2 Sn(C≡C‐R 2 ) 2 leads to boron‐functionalized 4‐stannabora‐cyclohexa‐2,5‐dienes although rather harsh reaction conditions (heating for a long period at 100–120 °C) are required when trialkylboranes (BR 3 ; R=Me, Et), Et‐9‐BBN, BPh 3 , and B(C 6 F 5 ) 3 are used . Organometallic‐substituted allenes obtained by 1,1‐organoboration of bis(trimethylstannyl)ethyne with trimethylsilyl‐ and dimethylsilyldialkylboryl‐substituted alkenes have been reported by Wrackmeyer .…”

“…The main product is the (Z)i somer. [22][23][24] The reaction is initiated by ac leavage of the polar metalÀcarbonb ond by the electron-deficient boron atom to form an alkynylboratelike zwitterionic intermediate, followedb yt he 1,2-shift of one organyl group from boron to the neighboring alkynyl carbon atom,l eadingt ot he organometallic-substituted alkene product substituted with an element from roup 14 of periodic table as wella ss ome other metals such as Ti andP t. [25][26][27][28][29] Early prog-ress was made by the conversion of BR 3 into trialkyl(alkynyl)borates [R 3 BÀCCÀCÀR 2 ] À ,f ollowed by their reactionw ith electrophilesa nd salt elimination57.T he application of alkenylmetalloidso rd ialkynylmetalloids in carboboration process is also an effective method for obtainingb oronate-substituted 1,3dienes 58 (Scheme 17).…”

Boron, aluminium, gallium, indium and thallium

“…91 The XE{1,2-Se 2 C 2 B 10 H 10 } (E = B or P, X = halide) clusters were synthesised and demonstrated to undergo alkyne insertion into the B-Se bonds of the borolane moiety. 92,93 Metallaboranes, metallaheteroboranes and exo-metallaheteroboranes A number of new transition metal centred boron molecular wheels have been observed, including [MrB 9 ] À (M = Rh or Ir, compounds VII and VIII) and [M 0 rB 10 ] À (M 0 = Nb or Ta), the first deca-coordinated 2D structures. 94 Photoelectron spectroscopy suggested that the former have stable neutral forms, MrB 9 .…”

Synthesis of Tellurasila Cycles Containing an Annelated Dicarba‐closo‐dodecaborane(12) Unit: Structure of a 1,4‐Ditellura‐2,3‐disilacyclohexane Derivative

“…Starting from the parent ortho ‐carborane 3 , careful preparation of 4 and 5 enabled the synthesis of diselenasila cycles in good yield and high purity,4c as shown for 6 in Scheme . Such diselenasila cycles turned out to be useful starting materials for the synthesis of other novel heterocycles, since the Si–Se bonds are readily split in exchange reactions with various element halides 20–22…”