Anthracenides

The a-naphthyldiphenylmethyl ether was prepared to protect, selectively, the 5 -OH group in nucleosides. It is prepared from a-naphthyldiphenylmethyl chloride in pyridine (65% yield), and cleaved selectively in the presence of a p-methoxy-phenyldiphenylmethyl ether with sodium anthracenide, a (THE, 97% yield). The p-methoxyphenyldiphenylmethyl ether can be cleaved with acid in the presence of this group. 

In practice the various trityl derivatives are cleaved with acid, but the monomethoxy derivative can be cleaved with sodium naphthalenide in HMPA (90% yield).It is not cleaved by sodium anthracenide, used to cleave a-naphthyldi-phenylmethyl ethers. 

Sulfonamides (R2NSO2R ) are prepared from an amine and sulfonyl chloride in the presence of pyridine or aqueous base. The sulfonamide is one of the most stable nitrogen protective groups. Arylsulfonamides are stable to alkaline hydrolysis, and to catalytic reduction they are cleaved by Na/NH3, Na/butanol, sodium naphthalenide, or sodium anthracenide, and by refluxing in acid (48% HBr/cat. phenol). Sulfonamides of less basic amines such as pyrroles and indoles are much easier to cleave than are those of the more basic alkyl amines. In fact, sulfonamides of the less basic amines (pyrroles, indoles, and imidazoles) can be cleaved by basic hydrolysis, which is almost impossible for the alkyl amines. Because of the inherent differences between the aromatic — NH group and simple aliphatic amines, the protection of these compounds (pyrroles, indoles, and imidazoles) will be described in a separate section. One appealing proj>erty of sulfonamides is that the derivatives are more crystalline than amides or carbamates. 

Biphenylbis(tricarbonyt)chromium (l).1 Lithium anthracenide converts biphenyl complexed by two Cr(CO), groups into a fairly stable dianion of structure 2, in which two V-cyclohexadienyl anions are coordinated with Cr(CO)3. This dianion is alkylated by an alkyl halide to form 3, in which one benzene ring is... 

Sc(OEP)C>2CMe is 0.4 s, which is the longest for any porphyrin, while the fluorescent yield of 0.2 is very high. The radiative properties are explained in terms of covalent interactions between the metal and the ring as modified by the probable location of the metal ion above the porphyrin plane.24 Scandium OEP complexes are reduced to the a, y-dihydro derivatives on reduction with sodium anthracenide and methanol.25 The redox potentials of Sc(OEP)OH have been determined by cyclic voltammetry to be ligand oxidation in PrCN, 1.03 and 0.70 ligand reduction in DMSO, —1.54 (Ey2 values in V vs. SCE) no metal redox wave was observed.26... 

Chlorins (2) are undoubtedly the most important dihydroporphyrins, since the chlorin chromophore is found in chlorophylls and some bacteriochlorophylls and, as the magnesium complex, is the catalyst in photosynthesis. The method of choice for formation of trans-chlorins involves reduction of iron porphyrins with sodium in boiling isopentyl alcohol (57JCS3461), but methods involving photochemical reduction of tin(IV) porphyrins, isomerization of phlorins, reduction of metalloporphyrins with sodium anthracenide followed by protonolysis, heating with sodium ethoxide, and photoreductions of zinc(II) porphyrins in the presence of ascorbic acid have also been employed. The best method for formation of c/s-chlorins (note that all natural chlorophylls possess the trans arrangement) appears to... 

Fe (Por)] is formed when Feni(Por) or Feu(Por) is electrochemically reduced or treated with a stoichiometric amount of sodium anthracenide in THF.89 [Fe TTP]" (Na-18-crown-6)+ (THF)2 is a tow-spin square planar complex jitK 2.5 BM, g x 2.1, 1.9, Fe—Npor 2.023(5) A), and shows a similar visible spectrum to that of Fe (TPP) but with a much lower intensity. This species is isoelectronic to Co (Por), the anionic charge, in addition to an odd electron to the dzl orbital, diminishes the ligand affinity of the iron atom. Further reduction generates an Fe"-porphyrin dianion. 

RSH, SnCl2 or ascorbic acid gives M(Chl) and M(iBchl) (M Zn) (Scheme 44). The hydrogens are introduced with a cis configuration. Chemically, M(Por) (M = Mn, Fe) can be reduced to traws-Chl with Na in refluxing amyl alcohol, while excessive reduction gives a mixture of Chi, Bchl and iBchl from which iBchl may be isolated in 40% yield (Scheme 45).166 Reduction of Zn(TPP) to Zn(TPC) with Na anthracenide has been reported.2... 

Reaction of dichloro(pentamethylcyclopentadienyl)silane with lithium, sodium or potassium naphthalenide gives a mixture of elemental silicon, the corresponding alkali metal pentamethylcyclopentadienide and decamethylsilicocene (82) (equation 64)181. Compound 82 is formed as the only product in the reduction of dibromo-bis(pentamethylcyclopentadienyl)silane with potassium anthracenide (equation 65)182. 

The complex is stable in air for a short time, but is sensitive to hydrolysis it melts at 171 °C without decomposition. From equations 64 and 65 it can be assumed that 82 is reduced by alkali metal naphthalenides, but not by potassium anthracenide, and this assumption was proved in separate experiments182. 

The reduction of bivalent aryltin chloride by sodium anthracenide in THF gave a new way to a bulky distannylanion in the form of a stable very close ion-pair (equation 54)71. The X-ray crystal structure reveals a normal Sn-Sn distance (2.81 A) in the distannylanion and a Sn—Na bond length of 3.24 A. 

Sodium anthracenide (1). The reagent is obtained by sonication of sodium and anthracene in DME. 

Magnesium anthracenide (9.10-dihydro-9,10-anthracenediyl)tris(tetrahydrofuran)magnesium) Mesitylmagnesium bromide (2,4,6-trimethyl-phenylmagnesium bromide) 4-Methoxyphenylmagnesium bromide Methylmagnesium bromide... 

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