Dimethoxymethane, protonated

As mentioned in the introduction, one of the major advantages of using transition metals for dearomatization is that they allow the isolation of reaction intermediates and, consequently, broaden the range of accessible manipulations. For example, when the naphthalene complex of [Os] (3) is treated with dimethoxymethane in the presence of HOTf, the resulting 3-lH-naphthalenium species 23 can be isolated in 88 % yield and stored for days at room temperature (Table 5). The electrophile adds anti to the face involved in metal coordination and pushes the proton at Cl toward the metal, which prevents spontaneous rear-omatization. As shown in Table 5, 23 reacts with MMTP, the conjugate base of dimethyl malonate, 2-trimethylsiloxypropene, tetrabutylammonium cyanoborohydride (TBAC), dime-... 

Triethylamine easily deprotonates the ring. The deprotio metalla-cyclobutadienes are more easily isolated after addition of pyridine ligands. Deuterium exchange on the p carbon of W(C3-/-Bu2D)[OCH(Cp3)2]3 with HOCH(Cp3)2 was demonstrated. Proton exchange probably occurs via elimination of DOCH(Cp3)2 and readdition of HOCH(Cp3)2. Even the presence of dimethoxymethane causes the elimination of HOCH(Cp3)2 [Eq. (206)]. In this case an equilibrium between the metallacyclobutadiene and its deprotonated counterpart could be observed. Por the phenyl-sub-... 

The idea of competition between the anomeric interactions is strongly supported by an ab initio study (67) on proton affinities of oxygens in the sc, sc and ap, sc conformers of dimethoxymethane (11) (Figure 3). Deslong-champs (7a) suggested that oxygens involved in o hyperconjugative... 

FIGURE 6.8 H NMR spectrum of dimethoxymethane with integration. The integration is the blue superimposed curve for each signal. The vertical height of the integral tells us how many protons of each type there are. Only a ratio can be obtained this way. 

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