Lithium Inflate

Although molecular rearrangements of carbohydrate inflates are rare, they are not unknown [2,21,31]. Many of these rearrangements are ring-contraction reactions associated with treatment of Inflates with lithium triethylborohydride [see Eq. (10) 20,21]. Reported rearrangement reactions occurring when halide or azide ions are the nucleophiles are quite rare and are restricted to epimerization at centers next to a carbonyl group. Such reactions have been reported only for the more basic fluoride [32] and azide ions (Scheme 5) [33],... 

One of the mildest methods for preparing methylene acetals involves reaction of a diol with dimethoxymethane in the presence of a suitable activating agent such as phosphorus pentoxide,176 trimethylsilyl Inflate.177 or lithium bromide and p-toluenesulfonic acid.178 The reaction is also used to make methoxymethyl ethers (see section 4.4,1) from alcohols. Scheme 3,95 illustrates the simultaneous formation of a methoxymethyl ether and a methylene acetal from Shikimic Acid.169 The reaction was adapted to the synthesis of the methylene acetal moiety of the marine antitumour agent Mycalamide B [Scheme 3.96],179... 

Di-r-butylmethylsilyl trifluoromethanesulfonate, f-Bu2MeSiOTf. The Inflate is obtained as an oil, b.p. 63-65 /15 mm, by reaction of f-Bu2MeSiH with triflic acid (95% yield). The reagent is used to prepare DTBMS esters and ethers, which are more stable than the t-butyldimethylsilyl counterparts. Thus the esters are not reduced by lithium t-butyldiisobutylaluminum hydride (10, 239-240) or hydrolyzed by acid, but are cleaved by BU4NR ... 

Vinyl Inflates.1 These triflates arc generally prepared by reaction of lithium cnolatcs with N-phenyltriflimide, (CFjSC NQHs, 12,395. These new pyridine-based triflimides arc considerably more reactive than N-phenyltriflimidc. 

Methyl ethers are usually prepared by some variant of the lliamson ether synthesis in which an alcohol reacts with either iodomethane. dimethyl sulfate, or methyl inflate (HAZARD) in the presence of a suitable base. A word of caution dimethyl sulfate and methyl triflate, like all powerful alkylating agents, are potentially carcinogenic and therefore should only be handled in a weil-ven-tilated fume hood. For the O-methylation of phenols (pKa 10) a comparatively weak base such as potassium carbonate in conjunction with dimethyl sulfate is sufficient, whereas simple aliphatic alcohols require stronger bases such as sodium hydride [Scheme 4.111] or lithium hexamethyldisilazide [Scheme 4.112]. The latter transformation is notable for the fact that O-methylation was accomplished without competing elimination. 

Allosedamine (113) and (+)-sedamine (119), two piperidine alkaloids isolated from Lobelia inflate, have been used for the treatment of respiratory disorders such as asthma, bronchitis, and pneumonia. While several racemic syntheses have been reported, there are much less asymmetric ones. An enantioselective route to (—)-aUosedamine (113) was developed by Raghaven et al, which commenced with addition of lithium compound 110 to the imine 109 providing the separable aUyUc amine 111 as a 3 1 mixture of diastereoisomers (Scheme 2.27) [45, 46). Six... 

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