“…Furthermore, the homobenzylic C−Ge bond thus formed was anticipated to be stable towards electrophiles, thereby preventing leaching of germanium-containing material during electrophilic ipso- degermylative library cleavage. It was initially envisaged that trichlorogermane/diethyl etherate complex , would be employed as the source of dichlorogermylene because of its simple preparation from inexpensive germanium(IV) chloride by reduction with tetramethyldisiloxane (TMDS). , Selective “capping” , of trichlorogermane 4 by careful control of the stoichiometry in reaction with a methyl Grignard reagent and the desired arylmetal “library precursor” (e.g., MeMgBr/ArLi, 2:1) would give arylgermane A and set the stage for Mitsunobu-type coupling to the resin (→ B ) (Scheme ). 1 …”
An efficient synthesis of chlorogermane linker 12 is described. Economic introduction of germanium into this linker is accomplished by insertion of dichlorogermylene [from germanium(IV) chloride] into the homobenzylic C-Cl bond of 4-(2-chloroethyl)phenol 1. Using linker 12, transmetalation with lithiated 4-acetophenone, 3-acetophenone, and 4-(4'methoxy)biphenyl followed by Mitsunobu-type coupling to Argogel gives functionalized resins 14, 16, and 18, respectively. Treatment of resin 18 with TFA, ICl, Br2, or NCS effects clean ipso-degermylation releasing biphenyls 19-22, respectively. Resins 14 and 16 are employed for the parallel synthesis of a library of pyrazoles by enaminone formation (using Bredereck's reagent), condensative ring-closure (using a series of monosubstituted hydrazines), and cleavage (using TFA and Br2). Analysis of this library reveals the influence of the hydrazine substituent on both the regioselectivity of ring-closure and the propensity for electrophilic substitution at the 4-position of the pyrazoles during ipso-degermylative cleavage.
“…Furthermore, the homobenzylic C−Ge bond thus formed was anticipated to be stable towards electrophiles, thereby preventing leaching of germanium-containing material during electrophilic ipso- degermylative library cleavage. It was initially envisaged that trichlorogermane/diethyl etherate complex , would be employed as the source of dichlorogermylene because of its simple preparation from inexpensive germanium(IV) chloride by reduction with tetramethyldisiloxane (TMDS). , Selective “capping” , of trichlorogermane 4 by careful control of the stoichiometry in reaction with a methyl Grignard reagent and the desired arylmetal “library precursor” (e.g., MeMgBr/ArLi, 2:1) would give arylgermane A and set the stage for Mitsunobu-type coupling to the resin (→ B ) (Scheme ). 1 …”
An efficient synthesis of chlorogermane linker 12 is described. Economic introduction of germanium into this linker is accomplished by insertion of dichlorogermylene [from germanium(IV) chloride] into the homobenzylic C-Cl bond of 4-(2-chloroethyl)phenol 1. Using linker 12, transmetalation with lithiated 4-acetophenone, 3-acetophenone, and 4-(4'methoxy)biphenyl followed by Mitsunobu-type coupling to Argogel gives functionalized resins 14, 16, and 18, respectively. Treatment of resin 18 with TFA, ICl, Br2, or NCS effects clean ipso-degermylation releasing biphenyls 19-22, respectively. Resins 14 and 16 are employed for the parallel synthesis of a library of pyrazoles by enaminone formation (using Bredereck's reagent), condensative ring-closure (using a series of monosubstituted hydrazines), and cleavage (using TFA and Br2). Analysis of this library reveals the influence of the hydrazine substituent on both the regioselectivity of ring-closure and the propensity for electrophilic substitution at the 4-position of the pyrazoles during ipso-degermylative cleavage.
“…1-6 Heteroadamantanes can also include other elements, predominantly from the IV, V, and VI Groups of the Periodical system; however, the proper ties of these compounds still remain poorly studied. [7][8][9] Heteroadamantane structures are convenient model systems for theoretical investigation of mechanisms of transfer of various intramolecular effects in framework molecules, which extends the known concepts on the nature of chemical bonds and electronic structure of carbo and heterocyclic compounds of complicated structure. 1,10, 11 The majority of known heteroadamantanes is repre sented by synthetic products.…”
The thermodynamic characteristics of adsorption (TCA) on the basal face of graphite have been calculated in terms of the semiempirical molecular statistical theory of adsorption for molecules of O , S , and Se containing heteroadamantanes of different structure and isostructural cyclohexane derivatives. The influence of the nature, number, and position of heteroatoms in the adamantane framework on the TCA values was studied in detail, which made it possible to predict the retention of the compounds considered on the surface of graphitized thermal carbon black under the conditions of equilibrium gas adsorption chroma tography. The introduction of each subsequent heteroatom into a polyheteroadamantane molecule makes a non additive contribution to the TCA values. The contributions of various fragments to the total adsorption energy were calculated by the TCA of isostructural heterocyclohexane molecules, and the most preferential orientations of the framework molecules of the adsorbates relative to the planar graphite surface were determined.
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