New cascade molecules centered about phosphorus

Abstract

Cascade molecules in which the branch points are phosphonium ion sites have been synthesized bearing phosphoms in a variety of oxidation states at the core. In addition to the previously reported phosphonium ion core species, these new cascade molecules include those bearing phosphine, phosphine oxide, and phosphorane cores. INTR 0 D U CTI ONA recent interest of our laboratory has been in the preparation and investigation of an intriguing category of molecules, cascade molecules (dendrimers, chemical fractals) [l] in which phosphorus has been incorporated at the core and branch points of the structure. Our efforts have been particularly concerned with the preparation and study of species in which phosphorus is present as phosphonium ion sites, rendering the covalent structure positively charged with "free floating" associated anions [2,3]. These species represent the first dendrimers bearing (charged sites within the covalent framework.The current efforts have been concerned with the preparation and investigation of dendrimers which retain the phosphonium ion branch points but are modified at the core to contain phosphorus in other oxidation states. Of specific interest are those with phosphine cores (accessible through the phosphine oxide or phosphine sulfide species) and those with phosphorane cores. Phosphine cores provide entry into the investigation of a wide range of chemical interactions, including those as nucleophile and metal complexation agent, modified by the presence of a large, highly charged ancilliary structure. A phosphorane core provides the first dendrimer involving pentadirectional elaboration from a single atom. RESULTS AND DISCUSSIONThe elaboration of all of the dendrimers considered in the present work begins with the previously reported trib-methoxymethy1)phenylphosphine. [2,3] The preparation of the phosphine oxide core dendrimer beginning with 1 is accomplished as shown in Scheme 1.Oxidation of the phosphine 1 to the phosphine

Regioselective Gold Complexation within the Cascade Structure of Phosphorus-Containing Dendrimers

“…Coordination of the free phosphine core of a phosphoruscontaining dendrimer of generation 2 with gold(i) was reported first. [2] Full coverage of the dendrimers with 16 and 32 w-phosphine chain-ends of generation 2 and 3 was accomplished with [Me 2 SAuCl]. [3] Recently, we prepared dendrimers containing thousands of terminal ÀP(Ph) 2 AuCl groups (generation 10); the gold complexes were imaged by highresolution electron microscopy.…”

“…[2] Full coverage of the dendrimers with 16 and 32 w-phosphine chain-ends of generation 2 and 3 was accomplished with [Me 2 SAuCl]. [3] Recently, we prepared dendrimers containing thousands of terminal ÀP(Ph) 2 AuCl groups (generation 10); the gold complexes were imaged by highresolution electron microscopy. [4] Therefore, gold can be introduced either at the core or on the surface of phosphorus-containing dendrimers.…”

“…All non-hydrogen atoms were anisotropically refined. Least-squares refinements were carried out by minimizing the function Sw( j j F o jÀj F c j j ) 2 , where F o and F c are the observed and calculated structures. A weighting scheme was used.…”

Polycations. 6. polycationic heterocyclic salts: Their synthesis and effect on double-stranded DNA

“…In fact, an upfield shift of 0.21 d is observed Both upper and lower limits are observed with regard to ring size for the facile formation of the polycationic heterocyclic salts. Attempts to generate polycationic heterocyclic salts by the general approach of addition of the ␣,x-dihalide to a solution of the ␣,x-ditertiary amine in acetonitrile fail when ␣,␣Ј-dibromo-p-xylene (1) is treated with 1,3-(dimethylamino)propane or with 1,12-bis(1-azonia-4-azobicyclo[2.2.2]octyl)dodecane dibromide (15). In these instances, the macrocycle, eleven-membered from 1,3-(dimephylamino) propane and twenty-six membered from 15), forms only to a limited extent (less than 40%) with most of the starting reagents yielding ionene polymer, relative amounts being estimable from 1 H NMR spectra.…”

Glycoside-Based Ionic Liquids

“…These "polycations" were of particular interest given our involvement in the construction and use for a variety of purposes of polyammonium and polyphosphonium salts. Polyammonium and polyphosphonium salts in several geometric categories were prepared, including dendrimers (Rengan & Engel 1990;Engel et al 1991;Engel 1992;Rengan & Engel 1992;Engel et al 1993a;Engel et al 1993b;Engel 1995;Cherestes & Engel 1994;Cherestes et al 1998), linear cationic arrays, "strings" (Fabian et al 1997;Shevchenko & Engel 1998;Strekas et al 1999;Engel et al 1999;Cohen et al 1998;Gordon et al 2006), and cyclic systems, "rings" Cohen et al 2000a;Cohen et al 2000b). Examples of these categories of polycationic species are illustrated in Figures Efforts using the cyclodextrins led to increasing interest in a variety of carbohydrate monoand polycationic species.…”