1‐Azonia‐2‐boratanaphthalenes

Abstract

The 1‐azonia‐2‐boratanaphthalenes (NH)(BX)C8H6 can be synthesized from 2‐aminostyrene and the dihaloboranes XBHal2 (1‐4: X = Cl, Br, iPr, tBu). Further derivatives (NH)(BX)C8H6 are obtained from 1 by replacing Cl by alkoxy or alkyl groups [5‐8: X = OMe, OtBu, Me, (CH2)3NMe2]. The hydrolysis of 1 gives a mixture of the bis(azoniaboratanaphthyl) oxide [(NH)BC8H6]2O (9) and the hydroxy derivative (NH)[B(OH)]C8H6 (10). The diboryl oxide 9 crystallizes in the space group C2/c. The lithiation of 4 at the nitrogen atom gives [NLi(tmen)](BtBu)C8H6 (11), which upon reaction with the diborane(4) B2Cl2(NMe2)2 yields the 1, 2‐bis(azoniaboratanaphthyl)diborane B2[N(BtBu)C8H6]2(NMe2)2 (12). The 2‐chloro‐1‐methyl‐4‐phenyl derivative (NMe)(BCl)C8H5Ph (13) of the parent (NH)(BH)C8H6 can be synthesized from the aminoborane BCl2(NMePh) and phenylethyne. Substitution of Cl in 13 gives the derivatives (NMe)(BX)C8H5Ph [14‐20: X = N(SiMe3)2, Me, Et, iBu, tBu, CH2SiMe3, Ph] and the reaction of 13 with Li2O affords the bis(azoniaboratanaphthyl) oxide [(NMe)BC8H5Ph]2O (21). The reaction of 16 or 19 with [(MeCN)3Cr(CO)3] yields the complexes [{(NMe)(BX)C8H5Ph}Cr(CO)3] (22, 23: X = Et, CH2SiMe3), in which the chromium atom is hexahapto bound to the homoarene part of 16 or 19, respectively. The complex 23 crystallizes in the space group P21/c. Upon reaction of the phenols para‐C6H4R(OH) with the aryldichloroboranes ArBCl2 and subsequent condensation of the products with phenylethyne, the 1‐oxonia‐2‐boratanaphthalenes O(BAr)C8H4RPh with R in position 6 and Ph in position 4 are formed (24‐26: Ar = Ph, R = H, Me, OMe; 27‐29: Ar = C6F5, R = H, Me, OMe). The azoniaboratanaphthalenes 1‐23 were characterized by NMR methods.

A Convergent, Modular Approach to Functionalized 2,1-Borazaronaphthalenes from 2-Aminostyrenes and Potassium Organotrifluoroborates

“…3,9 Paetzold synthesized 2,1-borazaronaphthalenes via a three component reaction employing aniline, an aryldichloroborane, and phenylacetylene (Scheme 1, IIA ). 10a As mentioned above, in early syntheses of N -substituted 2,1-borazaronaphthalenes, functionalization at nitrogen took place subsequent to ring formation in a second process under strongly basic reaction conditions. 8 However, Paetzold developed a different set of conditions for the synthesis of N -substituted 1,2-borazaronaphthalenes (Scheme 1, IIB ).…”

A Hybrid Organic/Inorganic Benzene

“…[8] Dewar and White pioneered the chemistry of monocyclic and ring-fused polycyclic 1,2-azaborine derivatives in the 1960s. [9] Recently, contributions by the groups of Ashe, [10] Piers, [11] and Paetzold, [12] as well as our group [13] have further advanced the preparation of novel BN heterocycles and sparked a renewed interest in the chemistry and properties of these compounds. [14] Despite the advances achieved to date, and given the powerful tools made available by modern chemical synthesis, it is surprising that a simple heterocycle such as the parent 1,2-dihydro-1,2-azaborine 1 has remained elusive.…”

BN versus CC: How Similar Are They?

“…6 and 7). [15,16] The Piers group has focused on the formation of heterocyclic analogues of the PAHs carbazole, phenanthrene (8), and triphenylene (9).…”