Xxvii oxides

Deoxy-sugars. Part XXVII. The Catalytic Oxidation of Some Derivatives of 2-Deoxy-D-hexoses, W. G. Overend, F. Shafizadeh, M. Stacey, and G. Vaughan,/. Chem. Soc., (1954) 3633-3634. 

Oxidation of the steroidal olefin (XXVII) with thallium(III) acetate gives mainly the allylic acetates (XXXI)-(XXXIII) (Scheme 15), again indicating that trans oxythallation is the preferred reaction course (19). Addition of the electrophile takes place from the less-hindered a-side of the molecule to give the thallinium ion (XXVIII), which by loss of a proton from C-4 would give the alkylthallium diacetate (XXIX). Decomposition of this intermediate by a Type 5 process is probably favorable, as it leads to the resonance-stabilized allylic carbonium ion (XXX), from which the observed products can be derived. Evidence in support of the decomposition process shown in Scheme 15 has been obtained from a study of the exchange reaction between frawr-crotylmercuric acetate and thallium(III) acetate in acetic acid (Scheme 16) (142). 

The cyclic voltammograms of the metal-dithiolene capped porphyrazines 147-149, 152, and 153 reveal a reversible oxidation couple arising from the peripheral [N2-M-S2] functionality, formally written as M(nyni) (M = Pt, Pd) (29). These oxidations occur at approximately +0.2 V (vs Fc+/Fc) for the Pd(bdt) (148), Pd(dmid) (149), Pt(tdt) (152), and Pt(dmit) (153) capped porphyrazines, respectively (Table XXVII). However, all... 

A somewhat similar configurational correlation between (leva)-glyceraldehyde and (dexfro)-lactic acid has been made by Wolfrom, Lemieux, Olin and Weisblat.36 Reductive desulfurization of tetra-acetyl-2-methyl-D-glucose diethyl thioacetal (XXVII) and hydrolysis of the product gave 2-methyl-l-desoxy-D-glucitol (XXVIII) oxidation... 

The positive charge on the transition metal in XXVII is a consequence of the tetravalent oxidation state of the transition metal in Cp2TiCl2. The active sites in traditional Ziegler-Natta polymerizations may be neutral because the transition metal is trivalent in those initiators (Secs. 8-4e, 8-4h-l). The group 3 metallocene initiators have neutral metal centers because those metals are trivalent. 

Products from the direct oxidation of lignin that give information about its structure include acetic, oxalic, and succinic acids, vanillin, vanillic acid, and dehydrodivanillin. Regarding lignin constitution, they are of only minor interest, but the yields in which they are obtained are significant. For vanillin and its derivatives the total yield is about 33% of spruce lignin (24, 36, 37, 38). Two extraordinary products of this direct oxidation deserve special attention—i.e., benzenepentacarboxylic (45) and tricarballylic acids (47), (XXIX) and (XXX). They will be mentioned later in connection with lignenolide (XXVII). 

Oxidation of the tris(pentamethyldisilanylmethyl)borane (XXVI) by alkaline hydrogen peroxide leads to the (hydroxymethyl)disilane, while reduction of the ethyl (pentamethyldisilanylmethyl)acetate (XXVII) with lithium aluminum hydride yields the (jS-hydroxyethyl)disilane. 

Hockett, Nickerson, and Reeder,91 using a very large excess of lead tetraacetate in acetic acid at 20°, observed an oxidation pattern for methyl a-D-mannofuranoside consistent with that noted by Criegee. One mole of reagent per mole was consumed very rapidly, and further oxidation was slow, as expected for the sequence XXV — XXVII. Presence of a small but finite amount of XXVI was thought to account for the slow, continuing oxidation. 

Condensation. Although aluminum alkoxides are effective in bringing about the mesityl oxide type condensation of ketones, as, for example, in the formation of dypnoue (XXVII) from acetophenone (XXVI),26 aluminum isopropoxide rarely induces this reaction to any significant degree in the reduction of ketones. 

Trimethyl-D-arabonolactone (XXVIII) has also been prepared from tetramethyl-D-fructofuranose (XXVI) by oxidation with nitric acid to give 3,4,6-trimethyl-2-keto-D-gluconic acid (XXVII), followed... 

Although the oxidation of RAs(OR>2 with selenium dioxide leads to the esters of the corresponding arsenic(V) acids, Wieber et al. (192) have shown that oxidation of the cyclic esters with SeC>2 in the presence of a diol results in compounds of type XXVII ... 

Also organic compound like metal phthalocya-nines [xxvi] and electronic conducting polymers [xxvii] are used as gas-sensitive layers in resistive sensors, POSFETs (polymer oxide silicon field-effect transistors), heterojunction diodes (e.g., polyrrole on... 

XXVII) which, being neutral, must contain both nitrogens in amide groups (34). This oxidation product, named methoxymethylchano-dihydrostrychnone, was found to be resistant to hydrolysis by concentrated hydrochloric acid. This observation was the cause of a long series of incorrect speculations, for it led to the conclusion that the newly formed amide group must be part of a cyclic amide or lactam system. 

Perbenzoic acid converts strychnine and dihydrostrychnine into the corresponding iV -oxides, with no attack on the C-21 to C-22 double bond at all (137). On the other hand, when the Nb is nonbasic, as in 18-oxo-strychnine, reaction occurs to give the C-21 to C-22 epoxide (CLXXVIII) (127). It is interesting to note that this epoxide is so sterically hindered to nucleophilic attack, that prolonged boiling with dilute sulfuric acid does not affect it. Methoxymethyldihydroneostrychnine (XXVI) is another molecule in which Nb is, if not nonbasic, at least very weakly basic in this case, too, perbenzoic acid cleaves the double bond to give methoxymethylchanodihydrostrychnone (XXVII) (34). 

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