Katecholboran

Katecholboran
Strukturní vzorec
Strukturní vzorec
Model molekuly
Model molekuly
Obecné
Systematický název2H-1,3,2-benzodioxaborol
Ostatní názvy7,9-dioxa-8λ2-borabicyklo[4.3.0]nona-1,3,5-trien, HBcat
Sumární vzorecC6H5BO2
Vzhledbezbarvá kapalina
Identifikace
Registrační číslo CAS274-07-7
EC-no (EINECS/ELINCS/NLP)205-991-5
PubChem6327445
SMILES[B]1OC2=CC=CC=C2O1
InChIInChI=1S/C6H5BO2/c1-2-4-6-5(3-1)8-7-9-6/h1-4,7H
Vlastnosti
Molární hmotnost119,91 g/mol
Teplota tání12,0 °C (285,2 K)[1]
Teplota varu50 °C (50 mmHg)
Hustota1,125 g/cm3
Bezpečnost
GHS02 – hořlavé látky
GHS02
GHS05 – korozivní a žíravé látky
GHS05
[1]
H-větyH225 H314[1]
P-větyP210 P233 P240 P241 P242 P243 P260 P264 P280 P301+330+331 P303+361+353 P304+340 P305+351+338 P310 P321 P363 P370+378 P403+235 P405 P501[1]
Teplota vzplanutí2 °C (275 K)
Není-li uvedeno jinak, jsou použity
jednotky SI a STP (25 °C, 100 kPa).
Některá data mohou pocházet z datové položky.

Katecholboran (zkráceně HBcat) je organoboran používaný v organické syntéze; jedná se o derivát pyrokatecholu a boranu se vzorcem C6H4O2BH.

Příprava a struktura

Katecholboran se původně vyráběl reakcí katecholu s boranem (BH3) v ochlazovaném tetrahydrofuranu; při tomto postupu se ovšem ztrácí dva ekvivalenty hydridu. Nöth a Männig vyvinuli vhodnější způsob spočívající v reakci borohydridu alkalického kovu (LiBH4, NaBH4 nebo KBH4) s tris(katecholáto)bisboranem za použití etherového rozpouštědla, například diethyletheru.[2] V roce 2001 zveřejnil Herbert C. Brown další postup, zahrnující reakci tri-O-fenylenbisborátu s diboranem, přičemž lze jako rozpouštědlo použít triglym nebo tetraglym. Tato metoda se vyznačuje 85% výtěžností a produkt 97% čistotou.[3]

Na rozdíl od samotného boranu nebo alkylboranů se katecholboran vyskytuje jako monomer. Tato vlastnost je důsledkem elektronových vlivů aryloxyskupin, které snižují Lewisovskou kyselost boru. Pinakolboran má strukturu podobnou.

Reakce

Katecholbotran v hydroboracích reaguje pomaleji než boran v tetrahydrofuranu (THF) nebo dimethylsulfidu (DMS).

Reakcemi katecholboranu s koncovými alkyny vznikají trans-vinylborany:

C6H4O2BH + HC2R → C6H4O2B-CHCHR

Produkty mohou být následně zapojeny do Suzukiových reakcí.[4][5]

Katecholboran lze použít jako stereoselektivní redukční činidlo pro přeměnu β-hydroxyketonů na syn-1,3-dioly.

Katecholboran se oxidativně aduje na komplexy kovů s nízkými oxidačními čísly, přičemž se tvoří borylové komplexy.[6]

C6H4O2BH + Pt(PR3)2 → C6H4O2BPt(PR3)2H

Reference

V tomto článku byl použit překlad textu z článku Catecholborane na anglické Wikipedii.

  1. ↑ a b c d https://pubchem.ncbi.nlm.nih.gov/compound/6327445
  2. ↑ Process for producing catecholborane - Patent 4739096
  3. ↑ New Economical, Convenient Procedures for the Synthesis of Catecholborane
  4. ↑ Janice Gorzynski Smith Organic Chemistry: Second Edition 2008 pp 1007
  5. ↑ MIYAURA, Norio; SUZUKI, Akira. Palladium-Catalyzed Reaction of 1-Alkenylboronates with Vinylic Halides: (1Z,3E)-1-Phenyl-1,3-octadiene. Org. Synth.. 1990, s. 130. DOI 10.15227/orgsyn.068.0130. 
  6. ↑ Emily C. Neeve; Stephen J. Geier; Ibraheem A. I. Mkhalid; Stephen A. Westcott; Todd B. Marder. Diboron(4) Compounds: From Structural Curiosity to Synthetic Workhorse. Chemical Reviews. 2016, s. 9091–9161. DOI 10.1021/acs.chemrev.6b00193. PMID 27434758. 

Externí odkazy

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