Synthesis and molecular structures of 1‐boracyclopent‐2‐enes

Abstract

The reaction of 1-silyl-1-borylalkenes with alkyn-1-yltin compounds affords borol-2-enes, organometallic-substituted allenes, mixtures thereof or even more complex mixtures with buta-1,3-dienes, depending on the third substituent at the C C bond (Bu or Ph), on the number of Si-Cl functions (two or three) and the nature of the alkyn-1-yltin compound. Six new borol-2-enes were isolated in pure state, and two of them were characterized by X-ray structural analysis. The solution-state structures of all major products were clearly established by multinuclear magnetic resonance methods ( 1 H,

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

“…Compound 9 a was isolated, albeit in rather low yield of 25 %. The isonitrile adduct 9 a shows two 11 B NMR resonances at d = 31.9 (BN) and d À20.5 ppm [BA C H T U N G T R E N N U N G (C 6 F 5 ) 2 ]. It shows the 1 H NMR resonances of a pair of different n-propyl groups and a singlet of the CNtBu ligand (d = 1.67 ppm).…”

“…. We have monitored two 11 B NMR resonances of compound 10 a at d = 57.6 (BN) and d À10.6 ppm, respectively. The iminium C=N IR band was found at 1640 cm À1 .…”

“…Workup gave compound 10 b as a white solid in 85 % yield. In solution, it shows 11 B NMR resonances at d = 56.8 (BN) and À9.9 ppm. The NMR spectra indicate that a boron-bonded iminium ion was formed [ 13 C NMR d = 185.6; 1 H NMR d = 2.64, 2.60 ppm (each 3 H)].…”

“…: 180 8C. 1 (5), b = 20.6425 (11), c = 15.1649 (10) , b = 104.625(3)8, V = 3487.1(3) 3 , 1 calc = 1.442 g cm À3 , m = 1.239 mm À1 , empirical absorption correction (0.807 T 0.855, Z = 4, monoclinic, space group P2 1 /n (No. 14), l = 1.54178 , T = 223(2) K, w and f scans, 44 522 reflections collected (AE h, AE k, AE l), [(sinq)/l] = 0.60 À1 , 5929 independent (R int = 0.061) and 4420 observed reflections [I > 2s(I)], 475 refined parameters, R = 0.078, wR 2 = 0.230, max.…”

“…[7,8] We have extended the application range of the 1,1-carboboration sequence to converting bisalkynyl phosphanes 2 into the respective phosphole derivatives 3 (see Scheme 2) by using B-A C H T U N G T R E N N U N G (C 6 F 5 ) 3 as the borane reagent, [9] and we have used BA C H T U N G T R E N N U N G (C 6 F 5 ) 3 for dihydroborole syntheses (e.g., 4 to 6). [10,11] This posed the question whether the reaction of a dialkynylborane derivative with BA C H T U N G T R E N N U N G (C 6 F 5 ) 3 might take a similar course that might eventually lead to the formation of a borole derivative. [12] Thus, in this study we have reacted two bisA C H T U N G T R E N N U N G (alkynyl)diisopropylaminoborane substrates (7 a, 7 b) with BA C H T U N G T R E N N U N G (C 6 F 5 ) 3 .…”