Organo‐substituierte Silole durch zweifache Organoborierung von Di‐1‐alkinylsilanen

Abstract

Organo‐Substituted Siloles by Twofold Organoboration of Di‐1‐alkynylsilanes Me2Si(CCR)2 [RMe (A), Bu (B), tBu (C), iPent (D), Ph (E), Me3Si (F)], prepared from Me2SiCl2 and MCCR (MLi, Na, K), react with Et3B by 1,1‐ethyloboration to form the organo‐substituted siloles Me2 (1a – f) in high yields with different reaction rates: F > B ≈︁ D > A > C > E. Me2Si(C CiPent)(C  CPh) (H) and Et3B give a 5 : 1 mixture of the two regioisomeric substituted siloles 2 and 2′. – 1a and e are deborylated with H2NCH2CH2OH or MeCO2H to 3a and e, respectively. 1a reacts with maleic anhydride to yield the [4 + 2] addition compound 4a. With (OC)5Fe, Cp‐Co(C2H4)2, and (CDT)Ni the cycloracemic (ligand)transition metal η41‐complexes [(OC)3Fe‐1a (5a), (OC)3Fe‐3a (6a), CpCo‐3a (7a)] and the cyclodiastereomeric η4,η41‐complexes Ni‐(3a)2 (8a/8a′) are formed. All products were characterized by multinuclear NMR, including measurements of J(29Si13C) and J(13C13C).

Combination of 1,2‐Hydroboration and 1,1‐Organoboration: A Convenient Route to 5‐Silaspiro[4,4]nona‐1,6‐diene Derivatives

“…Usually, the intermolecular 1,1-organoboration of alkyn-1-ylsilanes requires harsh conditions and long reaction times. [12,14] However, the intramolecular 1,1-organoboration proceeds fast and more smoothly, in most cases studied so far. [8][9][10]15] This is shown by the reactions of 1 or 2 with 9-BBN either in an equimolar ratio or with two equivalents of 9-BBN (Scheme 2).…”

Selective Synthesis of Stannoles by 1,1‐Carboboration of Bis(trimethylsilylethynyl)tin Compounds Using Weakly and Strongly Electrophilic Triorganoboranes: Characterization of a Zwitterionic Intermediate

“…[19] For instance, dialkynyl(dimethyl)silanes are converted quickly and selectively into siloles under mild reaction conditions, [20] whereas the analogous reaction with triethylborane requires heating at 100-110°C for several days. [21] The first attempts at using B(C 6 F 5 ) 3 for the 1,1-carboboration of dialkynyl(diorgano)-tin compounds other than 3 gave zwitterionic intermediates similar to 6(C 6 F 5 ) followed by the formation of 1,4-stannaboracyclohexa-2,5-dienes instead of stannoles. [9] Apparently, the Lewis acid strength of the B(C 6 F 5 ) 2 group in the elusive intermediates 5(C 6 F 5 ) has two functions: 1) It accelerates the migration of the alkynyl group from tin to boron to give 6(C 6 F 5 ) and 2) it stabilizes the zwitterionic intermediates 6(C 6 F 5 ) because of the relatively favored alkynylborate moiety (see Table 4 for relevant NMR spectroscopic data).…”

Metallacyclopentadienes and related heterocycles via 1,1‐organoboration of alkyn‐1‐ylmetal compounds

“…The 1,1-ethylboration of dialkyn-1-yl(dimethyl)-silanes of the type Me 2 Si(C C R 1 ) 2 with R 1 = alkyl, Ph, SiMe 3 [60], SnMe 3 [57] leads selectively to the siloles 40. Since prolonged heating at about 100…”

“…and the terminal positions in the molecule can be hydrogen (60,61), SiMe 3 (62,63,66) or SnMe 3 (63-65), or organyl groups (66) (Scheme 27). 1,1-Organoboration of such triynes or tetraynes can lead to novel siloles and fused heterocycles.…”