Cyclophane, meta

An unexpected varying regiochemistry in intramolecular benzannulation has also been observed in the synthesis of cyclophanes. As mentioned above, there are only two possible regiochemical outcomes in the benzannulation reaction, which differ in the direction of alkyne incorporation. / -Tethered vinyl-carbene chromium complexes undergo an intramolecular benzannulation reaction with incorporation of the tethered alkyne with normal regioselectivity to give meta-cyclophanes [28]. 

Yoshida et al. have reported the preparation of trisila[l.l.l]meta-cyclophane (trisilacalix[3]arene, 44) and tetrasila[l.l.l.l]metacyclo-phane (tetrasilacalix[4]arene, 45) (40) (Scheme 11) and indicate conformational analyses by using semiempirical MO calculations. 

Diethyl phosphate esters of the sterically congested phenols of calixarenes have been prepared in acceptable yields (>55%) and used in the preparation of meta-cyclophanes [8]. The corresponding reaction using diethyl phosphite, with triethylamine in place of the quaternary ammonium catalyst, results in only partial phosphorylation of the hydroxyl groups. 

H. Takemura, M. Kotoku, M. Yasutake, T. Shinmyozu, 9-Fluoro-18-hydroxy-[3.3]meta-cyclophane Synthesis and estimation of a C-F---H-0 hydrogen bond, Eur. J. Org. Chem. 9 (2004) 2019-2024. 

Fig. 1. Plane of Chirality Enantio-morphous figures and corresponding torsional angles A—X—Y—Z 7). Molecular examples ([n]paracyclophane, [2.2]meta-cyclophane, bridged[10]anulene and ( )-cyclooctene) with descriptors (/ , S)...

Fu, X., Hossain, M. B., Schmitz, F. J., and van der Helm, D., Longithorones, unique prenylated para-and meta-cyclophane type quinones from the tunicate Aplidium longithorax, J. Org. Chem., 62, 3810, 1997. 

Benzannulation is compatible with the construction of non-planar or strained aromatic rings. This is demonstrated by both the annulation of boat-like arene decks in [2.2]meta-cyclophanes and by an intramolecular benzannulation to form a hydroquinone deck itself. The first effort concentrated on the annulation of the strained ethene bridge in the [2.2]para-... 

The triple layered tetraazacyclophane (46) consisting of the unique crossed meta-meta cyclophane linkage was prepared and the enantiomers were separated by chiral HPLC (on a Daicel OD column). The CD spectrum of 46 was rather complex and seven Cotton effect peaks in the 190-280 nm region were observed [56]. Unfortunately, the four tosyl groups and the ester functions prevented the reasonable theoretical discussion and the assignment of absolute configuration. 

Although nowadays the term calixarene tends to be used for all [l ]-meta-cyclophanes, this chapter will deal with [l ]-metacyclophanes bearing phenolic OH groups in the intraannular (endo, e.g. calix[ ]arenes) or extraannular (exo, e.g. resorc[4]arenes) position. 

Similar [2.2]metacyclophanes 74a-k were obtained by pyrolysis as well [39]. The yields of these reactions vary without systematic pattern between 10 and 95%. Several tetrafluoro[2.2]metacyclophanes 76a,c,d and an octafluoro[2.2]meta-cyclophane with a completely fluorinated aromatic moiety 76b were also accessible by sulfone pyrolysis [40]. 

The linkage of two meta-cyclophanes by alkyne groups gave bis-cyclophane 106. Extraction experiments revealed a moderate binding of purine- and pyrimidine by these molecular tweezers [65]. The preferred conformation of [2.2]-metacyclophanes is the azzfz -arrangement [66]. Bodwell et al. [67] showed now that a 13-membered bridge levels the energy of syn- and anfz-conformer of 107. They slowly interconvert in solution at room temperature. 

Cyclopenten-l-ol, l,3-dimethyl-2-(7-methyl-3,7-tridecadien-ll-ynyl), , )-, 91-92, 279-280 2-Cyclopenten-1 -one, 3-methyl-2-(2-pentenyl)-, (Z)- (fasmone) synthesis, 29 2-Cyclopenten-l-ones syntheses by cyclizations from 1,4-dioxo compounds, 69, 79 from 5-nitro-l,3-diones, 81 Cyclophanes of porphyrins, 253 meta-Cyclophanes, 38, 338 pora-Cyciophanes = tricyclo[8.2.2.24,7]hexadeca-4,6,10,12,13,15-hexaenes synth., 38-39 Cyclopropane derivs. See Carbocycles, 3-membered... 

The chemistry of cyclophanes, the first representative of which, [2.2]meta-cyclophane was prepared by Pellegrin [1] as early as 1899, was first systematically studied in the 1950s, mainly by the innovative work of Cram [2]. Through specific syntheses, he prepared new members and recognized characteristic differences with regard to open chained benzene derivatives. 

K. -L Koike. M. Preparation and conformational studies of ethylene-bridge calixarene-analogous macrocyclic meta-cyclophanes. Chem. Ber. 1993. 126. 2501. 

In 2010, Collins and coworkers [62] developed additives to aid Ru-catalyzed olefin metathesis macrocyclizations (Scheme 12.36). The macrocyclization to form strained paracyclophanes is challenging, and control of the substrate conformation is often crucial toward ensuring product cyclization. As such, the authors developed a quinolinium-based additive that interacts with the substrate, enforcing conformations conducive to ring closure, even under elevated temperatures in the presence of a competing ir-rich solvent like toluene. The macrocyclization to form the [12] and [13]paracyclophanes 121, 122, 124, and 125 or the [12]meta-cyclophane 123 were all possible through the addition of the quinolinium salt 126 to the olefin metathesis reaction mixture. No macrocyclization products... 

CigHigOS, cis-2,4,9-Trimethylthioxanthene 10-oxide, 45B, 382 CigHigOS, cis-9-Ethyl-9-methylthioxanthene lO-oxide, 46B, 363 CigHigOS, cis-9-Isopropylthioxanthene 10-oxide, 41B, 411 CigHig02S2f 2,2-Diphenyl-1,3-dithiane cis-1,3-dioxide, 45B, 383 C1gH1gOftSg, 5,7,14,16-Tetramethoxy-1,2,3,10,11,12-hexathia[3.3]meta-cyclophane, 46B, 363... 

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