1,4-Naphthohydroquinone

As practiced by Hoffmann-La Roche, the commercial synthesis of vitamin is outlined ia Figure 1. Oxidation of 2-methylnaphthalene (4) yields menadione (3). Catalytic reduction to the naphthohydroquinone (5) is followed by reaction with a ben2oating reagent to yield the bis-benzoate (6). Selective deprotection yields the less hindered ben2oate (7). Condensation of isophytol (8) (see Vitamins, vitamins) with (7) under acid-cataly2ed conditions yields the coupled product (9). Saponification followed by an air oxidation yields vitamin (1) (29). 

These ethers can be removed from naphthohydroquinones either by elimination to the vinyl ether followed by hydrolysis or by Finklestein reaction with iodide followed by reduction with zinc. ... 

Methyl-1,4-naphthohydroquinone Phosphorus oxychloride Sodium hydroxide... 

Excellent diastereomeric ratios were achieved with terpene-derived auxiliaries. The pentacarbonyl[(-)-menthyloxycarbene]chromium complex 39 reacted with the sterically hindered 3,3-dimethylbut-l-yne to give tricarbonyl chromium naphthohydroquinone complex 40 in 81% de as the major diastereomer which was also characterised by X-ray analysis [41] (Scheme 25). Surprisingly, the application of other even more sterically demanding terpene auxiliaries or a variation of the alkyne did not improve the diastereomeric ratio [42]. 

Among the many phosphorus compounds selected by Mitchell and his collaborators may be mentioned tetrasodium 2-methyl l 4-naphthohydroquinone diphosphate (VTH). A concentration of 4 x 10 6 M of (VIII) produced a 50 per cent mitotic inhibition using chick fibroblasts in tissue culture. It is thought that the inhibition of the entry of cells into mitosis depends on the blockage of cellular synthetic processes involving phosphoryla-... 

The ansamycins (rifamycin B and rifamycin SV) are produced by certain strains of Nocardia mediterranei and act by inhibition of messenger RNA (m-RNA) synthesis, and consequently of bacterial protein synthesis. Structurally, they present a characteristic ansa structure, made of a ring containing a naphthohydroquinone system spanned by an aliphatic chain. The two ansamycins differ in the type of substituent on the... 

Stabilization of a radical anion of humic acid may be caused by an adsorption effect. Bijl (3) observed that solid barium hydroxide octahydrate turned blue when placed in a solution of quinhydrone the blue solid was highly paramagnetic. Under the conditions we used for preparing these salts, insoluble sodium humate (with a large surface area) could have stabilized the anion radical by adsorption from the basic solution. Weiss and McNeil (18) observed a similar phenomenon with base soluble xanthenes, and proposed that biradicals may be formed in such a system. His compounds, however, do not appear to have the structural requirements to satisfy such a stabilized system. The recent report by Weber (29) on the spin content increase associated with the basification of a naphthoquinone-naphthohydroquinone system seems to parallel our observations quite closely. 

The condensation of allylic alcohols with phenolic compounds in the presence of an acid catalyst yields allylphenols. This reaction was used 86 in a synthesis of vitamin K (LXXVa) by condensing phytol with 2-methyl-l,4-naphthohydroquinone in dioxane with oxalic or trichloroacetic acid as catalyst the hydroquinone first formed was oxidized to... 

Methyl-2-phytyl-2,3-dihydro-1,4-naphthoquinone 2-Methyl-2-phytyl-l, 2,-3,4-tetrahydro-l, 4-naphthohydroquinone u 94% 135... 

Furthermore, the successful [3+2+1] cycloaddition of alkynes bearing a cyclopropane ring and a carbene complex unit has been reported. These benzannulations result in the formation of bimetallic naphthohydroquinone chromium tricarbonyl complexes [48]. Additionally, (non-strained) cyclic alkynes are potent reaction partners in the cycloaddition of chromium carbene complexes [49]. 

Fig. 32. Individual and total packing densities for 1,4-naphthohydroquinone (NHQ) and 2,5,2, 5 -tetrahydroxybiphenyl (THBP) at a polycrystalline Pt electrode. O, NHQ , THBP , total. Experimental conditions NHQ concentration, 2.5 mM electrolyte, 1M HC104 temperature, 23 + 1°C. Reprinted from ref. 65.

Rifamycins B, O, S and X] (aliphatic bridge-spanned naphthohydroquinones) [Rifamycin SV]... 

The rifamycins were first isolated by Sensi et al.3) from Nocardia mediterranei as a complex mixture (Rifamycins A—E). Addition of diethylbarbiturate to the fermentation medium led to the sole production of rifamycin B6 which was obtained in crystalline form. Its structure has been determined by chemical7,and X-ray analysis9. The rifamycins might easily have excaped detection altogether, since rifamycin B has no antibacterial activity. However, it is spontaneously oxidized to rifamycin 0 and hydrolyzed to rifamycin S, a naphthoquinone derivative reduction yields the naphthohydroquinone derivative rifamycin SV (Fig. 4). These compounds inhibit the growth of Gram-positive bacteria at concentration as low as 0.0025 jug/ml. 

Naphthacenequinones, 19, 439 Naphthalene oxides, 130 Naphthazarin, 56, 57 Naphthohydroquinones, 368 1,4-Naphthoquinone, 18-19, 289 1-a-Naphthylethylamine, 320-321 1-(1-Naphthyl)ethyl isocyanate, 321 Nazarov reaction, 314, 499 Nerolidol, 292 Neryl acetate, 388 Nickel-Alumina, 321-322 Nickel boride, 190 Nickel(II) bromide, 136 Nickel(II) bromide-Zinc, 322 Nickel peroxide, 322-323 Nishimura catalyst, 408... 

BF3 Et20 is useful for the condensation of allylic alcohols with enols. A classic example is the reaction of phytol in dioxane with 2-methyl-l,4-naphthohydroquinone 1-monoacetate to form the dihydro monoacetate of vitamin Ki (Eq. 30), which can be easily oxidized to the quinone [57]. 

Supplier Aldrich Chemical Co. Geraniol can be used instead of expensive phytol it reacts with 2-methyl-1,4-naphthohydroquinone to give a product similar in chemical and physical properties to the natural vitamin and with pronounced antihemorrhagic activity. 

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