Phane derivatives

A new type of spiro-conjugated aminopyrans, pyrans, containing a cyclophane moiety 254, were obtained from a carbonyl[2.2]paracyclo-phane derivative 255 in a two-step procedure with isolation of UN 256 (03T1739) (Scheme 98). 

Other bridged derivatives are also known, examples being illustrated by the metacyclo-phane derivative (37) (74T2633), the thia crown ether (38) (74AG126) and the isomeric and separable cyclophanes (39) and (40) (74TL799). 

It has long been known that appropriately substituted [2.2]paracyclophanes are chiral, chemically stable and do not racemize under normal reaction conditions. With these seemingly ideal prerequisites for use in chiral synthesis, it is perhaps surprising that only three examples have appeared in the literature, all of them in recent years (Scheme 8). Reich employed [2.2]paracyclo-phane-derived selenides such as 24 to administer chirality transfer in selenoxide [2,3] sigmatropic rearrangements. Using this methodology, he was able to synthesize optically active linalool 25... 

The reaction has many synthetic applications. 4-Substituted anisole 189 was obtained from 2-methoxyenyne 188 using Pd(PPh3)4 and additional P(o-Tol)3, and the product was converted to 4-methoxyacetophenone 190 [58]. The intramolecular reaction is useful for the synthesis of various phane derivatives. Several oxaparacyclophanes 192 have been prepared from 191 using Pd(PPh3)4 and additional ligands in DMSO in good yields [59]. 

Another cycloaddition strategy for the synthesis of symmetrically substituted [2.2]paracyclo-phane derivatives involves the Diels-Alder reaction between bis-allene and disubstituted acetylenes (Scheme 16.38) [41]. The intermediate paraquinodimethide dimerized to form the cyclophane product, presumably through a diradical pathway. 

Hossain, M.K., Takeshita, M., and Yamato, T. (2005) Synthesis, stmc-ture, and photochromic properties of dithia(dithienylethena)phane derivatives. Eur. J. Org. Chem., 13, 2771-2776. 

Transannular coupling reactions have allowed access to the higher orthocyclo-phane derivative 87 [120, 121], the triply-bridged cyclophane 88 [122], as well as the highly distorted cone calix[4]arenes 89 (R = CH2CH20Et) [123] and 90 (R = nPr) [124]. 

The condensation reactions described above are unique in yet another sense. The conversion of an amine, a basic residue, to a neutral imide occurs with the simultaneous creation of a carboxylic acid nearby. In one synthetic event, an amine acts as the template and is converted into a structure that is the complement of an amine in size, shape and functionality. In this manner the triacid 15 shows high selectivity toward the parent triamine in binding experiments. Complementarity in binding is self-evident. Cyclodextrins for example, provide a hydrophobic inner surface complementary to structures such as benzenes, adamantanes and ferrocenes having appropriate shapes and sizes 12) (cf. 1). Complementary functionality has been harder to arrange in macrocycles the lone pairs of the oxygens of crown ethers and the 7t-surfaces of the cyclo-phanes are relatively inert13). Catalytically useful functionality such as carboxylic acids and their derivatives are available for the first time within these new molecular clefts. 

The synthesis of crystalline disodium derivatives of primary phos-phanes and arsanes turned out to be more difficult than that of dilithium compounds. The reaction of NaN(SiMe3)2 with 2c led, as in its lithiation with BuLi, under redox reaction (H2 elimination, As-As bond formation) to the Na2As6 dimer 12 (Eq. 5). The latter has been... 

It is a challenge to study dimetalated derivatives of primary phos-phanes that possess more covalent metal-phosphorus bonds. This can be achieved through replacement of the alkali metal ions in bimetallic phosphandiides by monovalent coin metal centers. 

Pye and Rossen have developed a planar chiral bisphosphine ligand, [2.2]PHANE-PHOS, based on a paracyclophane backbone (Scheme 1.6) [69]. Moreover, the ortho-phenyl substituted NAPHOS ligand, Ph-o-NAPHOS, has been successfully applied for the rhodium-catalyzed hydrogenation of a-dehydroamino acid derivatives [70]. 

Cross coupling between (—)-39 and the base 37 and subsequent transformation of the methyl group in the triple layered phane 41 yielded the [3]chochin derivative 42 which after a second cross coupling with (—)-39 gave a separable mixture of levo-rotatory [4]-, [5]- and [6]chochins (43, 44 and 45) ... 

The assignment of [(—)(kinetic resolution of its anhydride had to be revised to (—)(/ ) after application of the Byvoet-method to a derivative (60)106) (see 2.9.1.). (See also the results presented in Ref. 84) and discussed in Section 2.7.1). It therefore seems as if the general topology of [2.2]metacyclophanes is sufficiently different from that of paracyclo-phanes and 1,2-disubstituted metallocenes and therefore does not permit the application of the above-mentioned kinetic resolution method. 

While for several phanes such as [njparacyclophanes, dioxa[n]para or [2.2]meta-paracyclophanes, the assignments by this rule were in agreement with the experimental results, they had to be revised for [2.2]meta- and [m][n]paracyclophanes after the application of more reliable methods. These discrepancies were discussed in previous sections (2.6.1, 2.9.1). A quadrant rule proposed for cyclic ketones includes also the configurational assignment to oxo[2.2]metacyclophanes (61-63) and stereoisomeric alcohols derived therefrom 113). 

Lastly, mention should be made of an original scheme of access195 to an iminophos-phane (124) aminophosphorane (124a) equilibrium starting from PPh3 and an o-benzoquinone diimine derivative (125) (Scheme 30). 

The scope of this problem can be indicated by a brief consideration of the stereochemical nomenclature of hydroxy derivatives of the bicyclic terpenes. For the parent bicyclic hydrocarbon compound known in the literature at present as cam-phane, the name "bomane is recommended in this report. (Reasons for choosing "bornane are discussed later under "The Bornane Hydrocarbons .) A mono-hydroxy derivative of bornane, on the basis of IUPAC rules (41), would be named as a bornanol. Two such derivatives have the common terpene names, bomeol and isobomeol these names, on the basis of recommendations in this report would both become 2-bornanol. Obviously, this is inadequate and additional designations are necessary to distinguish between die two stereoisomers. 

The spectra of various disubstituted ferrocenes were examined by Clancy and Spilners (44) at low ionizing voltage, and they observed only the molecular ions. They have also used mass spectrometry to identify products from the reaction of lithioferrocene with benzyl chloride one of the products was dibenzylferrocene (189). The mass spectra of [5]-ferroceno-phanes show very intense molecular ion peaks and fragmentation is limited (9, 10). The ketone derivatives (LXXXT) and (LXXXII) fragment by elimination of carbonyl groups first. 

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