Unusual Pathway Taken in the Reaction of Bis(alkynyl)diisopropylaminoboranes with B(C₆F₅)₃

Abstract

The bis(alkynyl)diisopropyl-aminoboranes 7 were prepared by treatment of iPr2NBCl2 with two molar equivalents of 1-pentynyl lithium or lithium phenylacetylenide, respectively. Their reaction with one molar equivalent of B(C6F5)3 resulted in the formation of the 1,1-carboboration products 8 that were subsequently stabilized by adduct formation (9) with tert-butyl isocyanide. Thermolysis of 8a (R = nPr) proceeded with hydride transfer from a N-isopropyl substituent to the distal carbon atom of the remaining pentynyl unit at boron to give the zwitterionic five-membered heterocyclic product 10a in good yield. The analogous product 10b (R = Ph) was obtained upon photolysis of 8b. The compounds 7b, 9b, 10a, and 10b were characterized by X-ray crystal structure analysis.

Coordination Chemistry of Main Group Metals with Organic Isocyanides

“…[33] Erker and coworkers reported the carboboration product of bis (alkynyl)diisopropylaminoborane, which was characterized by forming the corresponding isocyanide adducts in 2013. [34] They synthesized compounds 31 a and 31 b by treating Despite the high binding energy of a triple bond, transition metal reagents and catalysts are well known to cleave a triple bond efficiently. Yamashita and co-workers have demonstrated the cleavage of the triple bond of an isocyanide functionality using unsymmetrical diborane 34 as a reagent, as shown in Scheme 15.…”

“…Erker and coworkers reported the carboboration product of bis (alkynyl)diisopropylaminoborane, which was characterized by forming the corresponding isocyanide adducts in 2013 [34] . They synthesized compounds 31 a and 31 b by treating iPr 2 NBCl 2 with the desired alkynyl lithium and in 1 : 2 equiv.…”

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).…”

Advanced 1,1-carboboration reactions with pentafluorophenylboranes

“…Instead it seemed that the sometimes observed typical carbocation pathway took over after the first 1,1-carboboration step and we eventually isolated the alternative product 57 (see Scheme 17). 43 …”