Nitroacrylates

The tryptophan side-chain can also be introduced using methyl 2-ethoxy-1-nitroacrylate as an clcctrophile[l 7b]. Vinylation occurs at room temperature by addition elimination. Reduction by SnCl2 followed by acylation generates A -acyl-o(, 3-dehydrotryptophans. 

Another approach is the Michael addition to ethyl (3-nitroacrylate, as shown in Eq. 7.123, which has been used in the synthesis of a-methylenebutyrolactone, a moiety characteristic of many sesquiterpenes. ... 

Recently, enhanced endo selectivity has been reported in the Diels-Alder reaction of fE -l-acetoxybuta-l,3-dienes with methyl fi-nitroacrylate The selectivity is compared with that of the reaction using l-methoxybuta-l,3-dienes and 1-trimethylsilyloxybuta-1,3-di-enes The degree of electron richness of a diene is an important consideration in endo eKO selectivity issues In particular, electron-rich dienes favor the formation of fixc-nitrocycload-ducts fEq 8 9 ... 

This procedure for the synthesis of ethyl 3-nitroacrylate is essentially that of Stevens and Emmons.2 Four major changes have been introduced by the submitters rapid introduction of dinitrogen tetroxide no purification of the intermediate nitro iodo ester use of dry, finely powdered sodium acetate for elimination of hydroiodic acid and percolation of the final product through a mat of alumina. With these modifications, the preparation is reproducible and highly efficient (80-90% overall). 

Ethyl 3-nitroacrylate is an extremely reactive receptor in the Michael reaction. It has found use in the synthesis of the a-methylene-butyrolactone moiety3 characteristic of many sesquiterpenes, as shown... 

The preparation of 5-ACETYL-l,2,3,4,5-PENTAMETHYLCYCLO-PENTADIENE is of value in the synthesis of pentamethyleyclo-pentadiene and many pentamethylcyclopentadienyl metal carbonyl derivatives that are more soluble in organic solvents than those derived from cyclopentadiene. Simple preparations of 5,6-DIHYDRO-2-PYRAN-2-0NE and 2-//-PYRAN-2-ONE make these hitherto rather inaccessible intermediates available for cycloaddition and other reactions. The already broad scope of the Michael reaction has been widened further by including an efficient preparation of ETHYL (E)-3-NITROACRYLATE. Workers in the field of heterocyclic chemistry will find a simplified method for the preparation of 2,3,4,5-TETRA-HYDROPYRIDINE of help. 

Ethyl nitrite, 58,113,115 ETHYL 7-3-NITROACRYLATE, 56,65 Ethyl JV-nitroso-JV-(p-tolylsulfonylmethyl> carbamate, 57, 96 Ethyl nonanoate, 59, 110 Ethyl 7-oxo-l-cycloheptene-l-carboxylate,... 

Esters and ketones bearing P-nitro groups can be prepared in many ways. For example, the Diels-Alder reaction of methyl P-nitroacrylate is one typical case. Various cyclic dienes are prepared by this route, and the reactions of Eq. 7.121167 andEq. 7.122168 are exemplified. 

Functionalized nitroalkenes are important dienophiles in the Diels-Alder reaction. For example, ( )-methyl P-nitroacrylate is an important reagent in organic synthesis. The nitro group can be readily eliminated the Diels-Alder reaction of P-nitroacrylate is equivalent to that of ethyl propiolate with an inverse regiochemistry (Eq. 8.4).11... 

In their pioneering work. Just and co-workers have described many interesting transformations of the Diels-Alder adducts of furan to methyl nitroacrylate (77 + 77 ) and to dimethyl acetylenedicarboxylate (53). The mixture of racemic adducts 77 + 77 was hydroxylated into the exo-cis-diols 125 + 125 , separable by crystallization. Treatment of the isopropylidene acetal obtained from 125 with diazabicyclo[5.4.0]undec-5-ene (DBU) gave a high yield of alkene 126. Ozonolysis followed by a reductive work-up with dimethylsulfide, then with NaBH4, gave a mixture of epimeric triols 127. Cleavage with sodium periodate afforded 2,5-anhydro-3,4-0-isopropylidene-DL-allose (128) in 15 % yield, based on methyl 2-nitroacrylate used. TTie same allose derivative was obtained from adduct 53. ... 

Martin NJA, Cheng X, List B (2008) Organocatalytic asymmetric transferhydrogenation of heta-nitroacrylates accessing beta(2)-amino acids. J Am Chem Soc 130 13862-13863... 

Reduction of 3-nitroacrylates 43 by Saccharomyces carlshergensis Old Yellow Enzyme is the key step in the synthesis of optically pure P-2-amino acids (Scheme 2.18). High yields and enantioselectivities of the initially derived nitro-compounds 44 were achieved. The latter can be further chemically elaborated to the corresponding P-amino acids 45 [20]. 

Racemic analogs of showdomycin have been synthesized from adducts (352 and 353) of methyl 2-nitroacrylate with furan. Synthesis of DL-2-ept-showdomycin involved treatment of the adducts with m-chloroperoxybenzoic acid, followed by nitrous acid elimination, to give the alkenic epoxide 379. Opening of the oxirane ring, and a sub-... 

The nitro derivatives were also obtained by direct synthesis starting from ethyl j8-ethoxy-a-nitroacrylate [Eq. (11)]. 

Acrylic acid and derivs 1 A96-A97 acrylic acid-trinitrophenylester 1 A97 acrylic esters, monomeric 1 A97 acrylic resins and plastics 1 A97 acryloylazide 1 A97 3-nitroacrylic acid 1 A97... 

Ethylacrylate and derivs 6 E201-E202 ethyl-2-nitroacrylate 6 E202... 

Nitro-4H-pyrimido[2,l-a]isoquinolin-4-one (241) was obtained via 240 in 68% yield when 1-aminoquinoline and ethyl 3-ethoxy-2-nitroacrylate were reacted in ethanol for 2 h at ambient temperature, and then the reaction mixture was evaporated in vacuo to dryness and the residue was cy-clized in polyphosphoric acid at 95°C for 50 min (77CB2480). 

Diels-Alder reactions have been conducted on solid phase, with either the dieno-phile or the diene linked to the support [156]. The reaction conditions and the regio-and stereoselectivities observed are similar to those in solution [58,157,158]. Illustrative examples of Diels-Alder reactions leading to support-bound cyclohexenes are listed in Table 5.10. Further examples include the cycloaddition of polystyrene-bound 2-sulfonyl-l,3-butadiene and V-phenylmaIcimidc [51], the high-pressure cycloaddition of 1,3-butadienes to resin-bound 1 -nitroacrylates [95], and the intramolecular Diels-Alder reaction of styrenes with acrylates [159]. 

Nitro-4//-pyrido[l,2-a]pyrimidin-4-ones 176 were prepared by the cy-clization of 6-unsubstituted 3-(2-pyridylamino)-2-nitroacrylates 175 (R1 = H) in polyphosphoric acid at 120°C for 1.5 hours in 50-63% yields [90JCR(S)308]. Instead of cyclizing, the 6-substituted derivatives 175 (R1 H) decomposed under these conditions. 

The a-addition of alkyl or aryl thionucleophiles R H to y9-nitroacrylates R2(NC>2) C=CC02R3 in THF in the presence of Et3N or DBU does not stop at y9-nitro-o -thioalkanoates R2CH(N02)CH(SR1)C02R3, but proceeds further with concomitant elimination of nitrous acid to afford a-thioacrylates R2CH=C(SR1)C02R3.191... 

Results of recent study, however, have been interpreted in terms of a homo-lytic process. Schechter and Conrad [49] have observed that the production of methyl-3-nitroacrylate and methyl-2-hydroxy-3-nitropropionate in the reaction between N204 and methyl acrylate could not be explained on the basis of heterolytic addition, but was to be expected if a homolytic process were occurring. Brown [80] has shown that olefin nitration under circumstances in which the nitronium ion (N02+) is the reactant has characteristics entirely different from those of the N204-olefin reaction. Brand and I. D. R. Stevens [81] also believed the reaction of addition of nitrogen dioxide to olefins to involve radicals. According to these authors the following experimental facts provide evidence for this ... 

The 13C- and H-NMR spectral data of a set of 2-acyl-2-nitroenamines are collected in Tables 31 and 32. The stereochemistry around C(1)=C(2) has been assigned by correlation with the NMR spectral properties of the corresponding enamines with a single electron-withdrawing group at C(2), or by comparison with compounds of fixed configuration, as those in Table 32. In the case of 3-amino-2-nitroacrylic esters (554... 

---