Paracyclophanes synthesis

Parachlorobenzotrifluoride, 6 1341 Paracortex, in wool fibers, 22 173 Para-crystalline lattice model, 24 464 Paracyclophane synthesis, 24 38 PARAFAC (PARAllel FACtor analysis),... 

Pischel I, Nieger M, Archut A, Vogtle F (1996) Chiral dithia[n]paracyclophanes - synthesis, crystal structure, and chiroptical properties. Tetrahedron 52 10043-10052... 

Tochtermann W, Ruckling D, Meints C, Kraus J, Bringmann G (2003) Bridged bioxepines and bi[10]paracyclophanes - synthesis and absolute configuration of a bi[10]paracyclophane with two chiral planes and one chiral axis. Tetrahedron 59 7791-7801... 

Jones developed a new fascinating method for [n]paracyclophane synthesis based on spiro carbene rearrangement. The first synthesis of la was achieved two decades ago by this method through rearrangement of the carbene species generated by thermolysis of the lithium salt of the spiro dienone tosylhydrazone 6 (Scheme 1) [1]. Although this work was epoch-making as the first synthesis of la, the formation of by-products hampered further study of la. 

Scheme 4. Anticipated paracyclophane synthesis using enyne metathesis macrocyciizations based on a removabie atropisomer controi eiement.

Yang TF, Chiu KY, Cheng HC, Lee YW, Kuo MY, Su Y (2012) Studies on the stracture of N-phenyl-substituted hexaaza [Ig] paracyclophane synthesis, electrochemical properties, and theoretical calculation. J Organ Chem 77(19) 8627-8633... 

Diederich, F., Dick, K., and Griebel, D. (1985) Water-Soluble Tetraoxa[n.l.n.l]paracyclophanes Synthesis and Host-Guest Interactions in Aqueous Solution Chem. Ber. 118, 3588-3619. 

Diederich, F. and Dick, K. (1985) A Water-Soluble Tetraoxa[7.1.7.1] paracyclophane Synthesis and Host-Guest Interactions with Alicyclic and Cationic Guest Molecules in Aqueous Solution , Chem. Ber. 118,3817- 3829. 

An example is the synthesis of substituted [2.2]paracyclophanes as reported by Hopfet al When hexa-l,2,4,5-tetraene 23 is treated with dimethyl acetylenedi-carboxylate 24 (an electron-poor acetylenic dienophile), the initially formed reactive intermediate 25 dimerizes to yield the [2.2]paracyclophane 26 ... 

As an illustrating example for the application of the Friedel-Crafts acylation in the synthesis of complex molecules, its use in the synthesis of [2.2.2]cyclophane 13 by Cram and Truesdale shall be outlined. The reaction of [2.2]paracyclo-phane 10 with acetyl chloride gives the acetyl-[2.2]paracyclophane 11, which is converted into the pseudo-geminal disubstituted phane 12 by a Blanc reaction, and further to the triple bridge hydrocarbon 13 ... 

A variant, the 1,6-Hofmann elimination, has become a standard method for the synthesis of [2.2]paracyclophanes 17 although it often gives low yields. 

Gade and Bellemin-Laponnaz have reported the synthesis, in good yields, of chiral oxazoline-imidazoliums salts 10a (Scheme 8) obtained by reaction of 2-bromo-4(S)-t-butyl oxazoline with several mono-N-substituted imidazoles [16]. Similaly an imidazolium salt 10b bearing a paracyclophane substituent was prepared by Bolm [17]. 

Topochemical [24-2] photoreactions of diolehn crystals has been reviewed. The reactions clearly depart from typical solution chemistry crystal-lattice control offers a unique synthetic route into photodegradable polymers, highly strained [24-2] paracyclophanes, stereoregular polymers, and absolute asymmetric synthesis. However, achieving the desired type of crystal... 

In order to study the role of the [2.2]paracyclophane-type planar chirality in asymmetric induction, Hou et al. have developed the synthesis of novel S/N-... 

Another impressive example is the synthesis of paracyclophanes as 4-9 by Hopf [3], starting from a 1,2,4,5-hexatetraene 4-6 and an electron-deficient alkyne 4-7 to give 4-9 via the intermediate 4-8 (Scheme 4.2). 

The photolysis of carboxylic acids and derivatives as lactones, esters and anhydrides can yield decarboxylated products 253>. This reaction has been utilized in the synthesis of a-lactones from cyclic diacyl peroxides 254) (2.34) and in the synthesis of [2,2]paracyclophane by bis-decarboxylation of a lactone precursor (2.35) 255). This latter product was also obtained by photoinduced desulfurization of the analogous cyclic sulfide in the presence of triethyl phosphite 256). 

The synthesis of [2.2]paracyclophane (2) and its identification by X-ray structural analysis were first reported in a short communication by Brown and Farthing 8> in 1949. A more detailed report on its molecular structure followed in 19534>. Further investigations by Lonsdale et al.5> at two different temperatures (93 and 291 °K) provided additional information about the thermal expansion and molecular vibrations in the crystal. A recent X-ray structural analysis > confirms and supplements Lonsdale s observations. 

During the synthesis of [2.2]paracyclophanediene, Dewhirst and Cram 83> prepared the bis-geminal dibromides 4a and 4b, which were subsequently converted into the diketones 5 a and 5 b. The UV spectra of the bromides 4a and 4 b show maxima at 236 nm. A comparison with the Amax values of other [2.2]paracyclophanes brominated at the bridges suggests that the absorption at 236 nm is the 235 nm band of [2.2]para-cyclophane, shifted bathochromically by the inductive effect of the... 

The occurrence of an additional two-membered bridge as intermediate in a [2.2]paracyclophane system has been postulated by Forrester and Ramasseul 47b>. During the synthesis of the bishydroxylamine 82, a precursor of the diradical 19 these authors were able to isolate as byproduct the pseudo-para hydroxy compound 83 which is converted into the violet quinone 84 through oxidation by atmospheric oxygen or reac-... 

In contrast, the results obtained in the methanolysis, acetolysis, and trifluoroacetolysis of the tosylate 91 were not the expected ones. Cram obtained the methyl ether 93, the acetate 94 and the trifluoro-acetate 95 with the same configuration and optical purity as in the direct synthesis from the alcohol 92. These solvolyses at the bridge carbon atom of [2.2]paracyclophane therefore proceed with complete retention of configuration. The rate of acetolysis of the tosylate 91 also deviates considerably from that of aliphatic secondary tosylates it is some 100 times faster than that of 2-butyl tosylate and about the same as that of a-phenylneopentyl tosylate, acetolysis of which is only slightly stereospecific. 

Less than two years after Chan and I disclosed the synthesis of 72 and 73, a more practical synthesis of 72 based on palladium-mediated reactions was reported by Armin de Meijere. I was deeply impressed by the highly efficient way Armin and his co-worker, Oliver Reiser, were preparing 72 as well as its derivatives. Immediately, I realized that it was impractical to compete with them. I therefore quit the dibenzo[2.2]paracyclophane field, with the strong conviction that many other unknown theoretically interesting molecules were still waiting for our pursuit. 

MacGillivray s group has employed rigid bifunctional molecules [42], such as 1,3-dihydroxybenzene and 1,8-naphthalenedicarboxyHc acid [42a], as linear templates to organize reactants such as fra s-l,2-bis(4-pyridyl)ethylene via hydrogen bonds for single and multiple photoinduced [2+2] cycloadditions, for the template-controlled synthesis of a l,2,3,4-(4-pyridyl)cyclobutane] [42b] and also of paracyclophanes [42d]. Very recently, [ ]ladderanes ( =2,3) have been synthesized in the solid state by UV irradiation of 2(5-methoxyresorci-nol) 2(4-pyr-poly-m-ene) (m=2,3) [42e]. 

An enantioselective biomimetic synthesis of longithorone A was accomplished on the basis of proposed biosynthesis. " The syntheses of two [12]-paracyclophanes 105 and 107 are realized by applying ene-yne metatheses macrocyclization to 104 and 106, which are synthesized from the common substrate 103. Longtholone A is constructed using intermolecular and transannular Diels-Alder reactions followed by oxidation (Scheme 40). 

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