4347-31-3Relevant articles and documents
On the directing effect of boronate groups in the lithiation of boronated thiophenes
Borowska, Elena,Durka, Krzysztof,Lulinski, Sergiusz,Serwatowski, Janusz,Wozniak, Krzysztof
experimental part, p. 2208 - 2218 (2012/06/01)
An investigation of thiophene boronates has revealed the usefulness of a metalation reaction in the synthesis of various lithiated thiophene boronates, which were further converted to functionalized thiopheneboronic derivatives. The lithiation of 2- and 3-thienylboronic N-butyldiethanolamine (BDEA) esters with lithium diisopropylamide and lithium 2,2,6,6-tetramethylpiperidide showed that both boronated thiophenes were readily deprotonated. In the latter case, lithiation at the 2-position adjacent both to sulfur and the borocanyl group is thermodynamically favoured due to the significant stabilizing effect of the borocanyl group. Further derivatization with a range of electrophiles followed by hydrolysis afforded various 2-substituted 3-thiopheneboronic acids. Lithiation of the corresponding thiopheneboronic "ate" complexes of the type [ThB(OR)3]Li revealed that the 2-thienyl derivatives could not be effectively deprotonated, whereas the "ate" complex, [3-ThB(OEt)3]Li, was selectively lithiated with nBuLi at C-2. This points to a directing effect of the anionic boronate moiety. The resulting bimetallic species, [(2-Li-3-Th)B(OEt)3]Li, underwent ring-closing dimerization upon heating to give, after subsequent hydrolysis, 4,8-dihydro-4,8-dihydroxy-p-diborino[2,3-b:5,6-b′]dithiophene - a cyclic diborinic acid. A computational study of the lithiation of boronated thiophenes and furans proved that boronation decreases ring-proton acidity. This effect is much stronger for the boronic "ate" complexes than for the corresponding neutral BDEA esters. Calculations of the transition states have shown that the specific directing effect of boronate groups in 3-thienyl derivatives is due to intramolecular oxygen-lithium coordination.
Propanoic acid derivatives
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, (2008/06/13)
Propanoic acid derivatives of formula (1) are described: Ar—X1—Ar1—Z—R??(1) in which Ar is a nitrogen base containing group; X1is linker atom or group; Ar1is an optionally substituted 5- or 6-membered nitrogen-containing aromatic or non-aromatic monocycle; Z is a group —CH(R13)CH2— [in which R13is an optionally substituted aliphatic, cycloaliphatic, heteroaliphatic, heterocycloaliphatic, aromatic or heteroaromatic group], —C(R12a)(R13)—CH(R12b)— [in which R12aand R12btogether with the carbon atoms to which they are attached form a C3-7cycloalkyl group] or C(R13)═CH—; R is a carboxylic acid (—CO2H) or a derivative or biostere thereof; and the salts, solvates, hydrates and N-oxides thereof. The compounds are able to inhibit the binding of αVintegrins to their ligands and are of use in the prophylaxis and treatment of immune or inflammatory disorders.
