From nitroalkenes

Introduction of fluorine by oxirane-ring opening is described first. The 1,2-oxirane 408, prepared from nitroalkene 407 and hydrogen peroxide, was treated with KHF2 (ethylene glycol, 20 min, 112°) to 2-... 

Intramolecular Cycloaddition Intramolecular nitrile oxide cycloaddition (INOC) is widely used in the synthesis of various compounds, particularly, natural products. This field is reviewed in detail in Chapter 6 of the mono-graph/Reference 5 and also in Reference 400 limited to nitrile oxides generated from nitroalkenes. Some features of INOC are illustrated in this subsection by new data and those omitted in Reference 5. 

In this approach, the SENA skeleton is assembled from nitroalkene (42) and nucleophile 56.With the exception of two examples (entries 1 and 2 in Table 3.2), the reaction does not stop at SENA 51, which either undergoes intramolecular cyclization through [3 + 2]-cycloaddition to give fused heterocycles (as a rule after elimination of trimethylsilanol) (198-200) or is involved in [3+ 2]-cycloaddition with specially added methyl vinyl ketone or methyl acrylate to form (after elimination of silanol) substituted isoxazolines in rather high yields (201). 

The d5,cw,c ,c -[5,5,5,5]-l-azafenestrane as complex with BH3 (261) was prepared starting from nitroalkene (262), which is difficult to synthesize, using an approach shown in Chart 3.18 and Scheme 3.172. (429)... 

Diketones are produced from nitroalkenes and the lithium enolates of ketones. Equation 132 shows the reaction of the enolate of 2-hexanone with 2-nitropropene in the presence of acetic anhydride. The resulting betaine 409, a greenish-blue liquid, is hydrolysed to the diketone by successive treatment with boron trifluoride and water441. 

Spurred by these observations, we examined a relevant application of the method for nitrocyclopropane synthesis from nitroalkenes and dimethylsulfoxonium methylide (17), Equation 3. It had previously been employed for the synthesis of a 2,3-dideoxv-2,3-C-methylene-3-nitro-hexopyranoside, the first one of the small number of carhohvdrates containing the nitrocyclopropane structure thus far known (18). 

Most of the current preparative methods of oximes from nitroalkenes are not versatile. Reduction of nitroalkenes by CrCl2 or NaH2P02 in the presence of palladium was reported to afford the corresponding oximes, but the yields are not satisfactory. Zn-acetic acid and Na2Sn02 reductions are limited to the preparation of ketoximes only. Electroreduction of alkenes was reported to yield mixmres of ketones and ketoximes, or oximes and acetals (or ketones) depending on the strucmre of nitroalkanes. 

Typically, oc,0-unsaturated esters, a,0-unsaturated aldehydes and a,0-unsaturated nitriles are poor acceptors for the Lewis acid catalyzed silylallylation procedure, but they are excellent acceptors for the complementary fluoride ion mediated allylation procedure (cf. Volume 4, Chapter 1.2, Section 1.2.2.1.7). Other suitable acceptors include 1,4-quinones,70 a,0-unsaturated acyl cyanides (162),718 silyl ot,0-enoates (163)71b and nitroalkenes (Scheme 26) 72 reduction (titanium(III) trichloride) of the intermediate nitronates arising from nitroalkene allylation affords y,8-enones (166). 

Cyclizations of the nitrile oxide derived from nitroalkene (71) also led to bicyclic isoxazoline (72) as one stereoisomer, presumably through a transition state that minimized A1 -strain (Scheme 20).3S Re-... 

Several new examples of the Barton-Zard pyrrole synthesis from nitroalkenes and isocyanoacetate esters demonstrate the broad utility of this procedure. An excellent yield of ethyl 3-(9-anthryl)-4-ethylpyrrole-2-carboxylate was obtained starting with the nitroalkene from anthracene-9-carboxaldehyde and 1-nitropropane. <95TL8457> Bums et.al. reported an improved synthesis of benzyl isocyanoacetate which facilitates the synthesis of benzyl pyrrole-2-carboxylate esters by this method. <95SC379> 3-(l-Arylpyrrol-2-yl)pyrrole-2-carboxylates were prepared from l-aryl-2-(nitrovinyl)pyrroles. <95JHC 1703>... 

Diels-Alder cyclizations are thermal reactions, and recent significant developments in the use of microwave irradiation to pyridine synthesis have been reported, including a series of pyrazolo[3,4- ]pyridines from nitroalkenes and pyrazolylimines with reaction times of 5-10min (Equation 115) <2000T1569>. This method appears to be general to this bicyclic class for example, replacement of the substituent on the imine allows for a C-2-unsubstituted pyridine. A range of cyclic and acyclic dienes have also been reported. 

R)-(-)-2,2-Diphenylcyclopentanol (1) is a highly effective chiral auxiliary in asymmetric synthesis. Hydrogenation of chiral 0-acetamidocrotonates derived from this alcohol has afforded the corresponding 0-amido esters with high diastereoselectivity (96% de).6 In addition, (R)-1 has been used as a chiral auxiliary in Mn(lll)-based oxidative free-radical cyclizations to provide diastereomerically enriched cycloalkanones (60% de).7 Our interest in (R)-(-)-2,2-diphenylcyclopentanol is its utility as a chiral auxiliary in Lewis acid-promoted, asymmetric nitroalkene [4+2] cycloadditions. The 2-(acetoxy)vinyl ether derived from alcohol (R)-1 is useful for the asymmetric synthesis of 3-hydroxy-4-substituted pyrrolidines from nitroalkenes (96% ee).8 In a similar fashion, a number of enantiomerically enriched (71-97% ee) N-protected, 3-substituted pyrrolidines have been prepared in two steps from 2-substituted 1-nitroalkenes and (R)-2,2-diphenyl-1-ethenoxycyclopentane (2) (see Table).9... 

BuLi and AC2O of nitrooxaheptynes 20, generated in high yields from nitroalkenes and hydroxy alkynes <03H(59)685>. 

Intramolecular reactions of nitronic acids, obtained from nitroalkenes and acetoacetate, lead to furans or /V-substituted pyrroles, depending on the organic base which is used (Scheme 54). ... 

Diamines. A synthesis from nitroalkenes is through Michael addition followed by catalytic hydrogenation. 

Anions derived from nitro compounds are characterized by a broad range of nitrogen chemical shifts (Table XXVI). There is no significant difference between the shifts of the NOz moiety of nitro derivatives of azoles and the corresponding sodium or potassium salts, but anions derived from nitroalkenes show a considerable increase in the nitrogen shielding when compared with the parent compounds. 

Aldehydes from nitroalkenes. By using Al-NiCl2-6H20 in THF, nitroalkenes are converted into aldehydes (9 examples, 60-88%). 

Magnesium-cadmium chlori Reductions. A number c tern, which includes acid chio pounds. THF is used as cosolvx Ketones from nitroalkenes... 

Ketones from nitroalkenes. Some selectives are observed. 

Ketones from nitroalkenes. The reduction also enables the assembly of spiroacetals using the Nef condensation. 

Ketones from nitroalkenes. NaH PO ence of a catalyst. Its combination with Rai tones has been put to use in the general s> t rom functionalized nitroalkanes. 

Nitroalkanes from nitroalkenes. The reduction of the conjugated double bond with NaBHjCN is catalyzed by a zeolite (H-ZSM-5) in MeOH at room temperature (10 examples, 65-79%). 

More recently, Dong s group developed a palladium-catalyzed synthesis of indoles from nitroalkenes [43]. This was the first report on transition metal-catalyzed transformation of conjugated nitroalkenes into indoles. Under mild reaction conditions (1 bar carbon monoxide, 110 °C), palladium catalyzes the reductive cyclization of nitroalkenes to form a putative nitrosoalkene intermediate, which then rearranges to provide 3-arylindoles in high yields (Table 9.5). Notably, this novel C-H bond amination takes advantage of carbon monoxide as an inexpensive stoichiometric reductant and produces carbon dioxide as the major byproduct. 

Nitroalkanes have also been synthesized from nitroalkenes/ amines/ or bromides and by selective additions of nitro-compounds to methylenemalonate... 

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