Bistetracyclones and Bishexaphenylbenzenes. II

Abstract

VOL. 20 ~i t y .~ Since the tendency of amino compounds to form complexes with silyl groups with less than three Si-0 bonds is negligible,lO the effects seen here would be expected only in the case when R = (MeO)aSiCH2-Other possible interactions could involve intramolecular hydrogen bonding with the imino nitrogen and a silanol as in VI1 or silicon-oxygen bond formation with the 2-carbon atom of the ring (VIII). In the latter case the intermediate B would result after hydrolysis of the silicon-oxygen-carbon bond. These intermediates resemble those advanced to explain the enhanced rates of hydrolysis for certain a-keto phos-CHzCHz. (10) See, for example. C. Frye. G. E. Vogel, and J. A. Hall, J . Am, Chem. 6". , 88, 9913(1981).-Sl VI1 VI11 phate esters" and p-nitrophenyl salicylates.12 However, with such interactions all of the methoxysilanes studied should show effects similar to V unless an unusual acidity for the corresponding silanol of V is postulated to explain its unique behavior.Six additional representatives of the class of colored compounds, the bistetraphenylcyclopentadienones (l), have been prepared linked by (CHZ)~, (CHZ),, (CHZ)4, (CHZ)~, and (CH& respectively, and one in which one of the phenyl groups links two cyclopentadienone rings. New intermediates for their syntheses have been described including the required bisdeoxybenzoins and bisbenzils. Analogs of hexaphenylbenzene, melting in the range 337-470", were prepared from each bistetraphenylcyclopentadienone by reaction with tolan. The absorption spectra of bistetracyclones and bishexaphenylbenzenes have been discussed based on tetracyclone and hexaphenylbenzene as models.(7) G . M. Mkryan and N. A. Papazyan, Doki. Akad. Nauk Arm. SSR, 91,

Organic and organometallic derivatives of pentaphenylbenzene, C6Ph5X: correlation of peripheral phenyl ring orientations with the steric bulk of “X”

“…16 1-Phenylethynyl-2,3,4,5,6-pentaphenylbenzene (3) was originally synthesized by Dilthey et al in 1935 17 by heating together tetracyclone and 1,4-diphenyl-1,3-butadiyne at 250°C under a nitrogen atmosphere; the loss of carbon monoxide from the Diels-Alder adduct yields Ph-C'C-C 6 Ph 5 (3) directly. A second, albeit sterically very demanding, [4+2] cycloaddition furnishes decaphenylbiphenyl, Ph 5 C 6 -C 6 Ph 5 (4), as reported by Ogliaruso and Becker in 1965; 18 the acute steric crowding was confirmed by Pascal and co-workers only in 1988 as part of a comprehensive X-ray crystallographic study of highly congested polycyclic aromatic hydrocarbons. 19 Surprisingly, perhaps, the X-ray crystal structure of pentaphenylbenzene (2) appears not to have been previously reported and is shown in Fig.…”

“…It is likely that 17 arose during the acidic workup, and a possible mechanism involving a cyclic intermediate is depicted in Scheme 4. The lengthening of the side chain in 16 removes the steric problems associated with the directly attached alkyne in 1-phenylethynyl-2,3,4,5,6-pentaphenylbenzene 3 and allows ready formation of the tetrahedral dicobalt cluster (C 6 Ph 5 -CO 2 -CH 2 -C'CH)Co 2 (CO) 6 (18).…”

Bio micro fuel cell grand challenge final report.

“…28 29 30 31 32 33 This has generated mostly PEM's with lower costs and improved thermal stability, but generally lower ionic conductivities at comparable ion exchange capacities than Nafion. 34 However, many of these thermoplastics based PEMs are more susceptible to oxidative or acid catalyzed degradation than Nafion. 35 Utilizing a purely aromatic polymer, such as poly(phenylene)s, provides a route to potentially improve the thermochemical stability of PEMs due to their inherent thermochemical stability.…”

Semi‐fluorinated polyarylenes: Microwave‐assisted synthesis and structure–property relationships

“…Diels–Alder step‐growth polymerization has been utilized for the synthesis of a variety of polymers 25 . More specifically, bistetracyclone dienes, containing cyclopentadienone moieties, react with bisphenylacetylenic dienophiles to afford phenylated polyphenylenes or polyarylenes with carbon monoxide as a byproduct 26–30 . In these Diels–Alder reactions (Scheme 1), both para ( 1 ) and meta ( 2 ) products are possible, and early model studies pointed toward meta being preferred 30 .…”