1- alkoxy-3-nitroalkanes

Nitronates derived from primary nitroalkanes can be regarded as a synthetic equivalent of nitrile oxides since the elimination of an alcohol molecule from nitronates adds one higher oxidation level leading to nitrile oxides. This direct / -elimination of nitronates is known to be facilitated in the presence of a Lewis acid or a base catalyst [66, 72, 73]. On the other hand, cycloaddition reactions of nitronates to alkene dipolarophiles produce N-alkoxy-substituted isoxazolidines as cycloadducts. Under acid-catalyzed conditions, these isoxazolidines can be transformed into 2-isoxazolines through a ready / -elimination, and 2-isoxazolines correspond to the cycloadducts of nitrile oxide cycloadditions to alkenes [74]. 

The acylation of the carbanions derived from nitroalkanes with acyl imidazoles or alkoxy-carbonylimidazoles takes place at the carbon atom to yield a-nitro ketones or a-nitro esters, respectively (Eq. 5.10).21 The lithium salts of nitroalkanes were isolated and used in THF or DMSO in the original procedure. Later, potassium salts generated in situ on treatment with r-BuOK in DMSO are reactive enough to give a-nitro ketones in good yield (Eq. 5.11).22... 

Nitronates, particularly silyl nitronates, are often superior to nitrile oxides in their 13DC with olefins in terms of their ease of generation from nitroalkanes, stability, and the observed selectivity during cycloaddition. Cycloaddition of alkyl or silyl nitronates with olefins generates N-alkoxy- or N-silyloxy-substituted isoxazolidines which then undergo spontaneous or acid catalyzed elimination of alcohol (or silanol) to produce isoxazolines (see Scheme 1, Sect. 2). 

The y-stannylcarbenium ion formed is stabilized by homoconjugation of the carbon-tin bond and undergoes destannylative cyclization leading to cyclopropane (25) (Scheme 9.22). In the presence of (la), N,N-bis(siloxy)enamines, prepared by double silylation of nitroalkanes, react with acetals to give l-alkoxy-3-nitroalkanes [76]. 

---