Vinylogous esters and amides

I, 5-dicarbonyl compounds and their interesting and varied chemistry, e.g., the formation of cyclohexenones from aldol condensation of the products. As an extension of the de Mayo reaction (the photocycloaddition of enolated /i-diketones to double bonds) enol esters, enol ethers, vinylogous esters and amides, and dioxinone have been employed as the enone components. Some intermolecular examples have already been discussed in Section 1.6.1.4.2.1.6. (cf. Table 4, entries 2 and 3) and some intramolecular systems are collected in Table 5, entries 10,... 

II, 14, 15. Here intramolecular cycloadditions of enol esters, dioxinones and vinylogous esters and amides as /1-diketone equivalents will mainly be discussed. The examples shown belong to the de Mayo reaction in the broader sense as mentioned above. For more details see references 12 and 13. 

By analogy with cyclopropanes and oxiranes, 2-acylaziridines, aziridine-2-carboxylic esters and amides, are also suitable substrates for one-electron reductive ring cleavage. This is an efficient and highly regioselective method for the synthesis of yS-amino carbonyl compounds. Vinylogous substrates are, furthermore, transformed into <5-amino y8,y-unsaturated carbonyl derivatives azetidines can also be used to achieve y-amino functionalization (Scheme 19) [72]. 

The addition of isocyanides and azide to aldehyde-derived enamines has led to tetrazoles (533,536). On the other hand the vinylogous amide of acetoacetic ester and related compounds reacted with aldehydes, isocyanides and acids to give a-acylaminoamides (534). Iminopyrrolidones and imino-thiopyrrolidones were obtained from the addition of cyclohexylisocyanide and isocyanates or isothiocyanates to enamines (535). An interesting method for the formation of organophosphorus compounds is found in the reactions of imonium salts with dialkylphosphites (536). 

The unified highly convergent total and formal syntheses of ( + )-macro-sphelides B (441 X = O) and A (441 X = a-OH, p-H), respectively, have been described (483). Key features of the syntheses include the concise synthesis of the optically active S-hydroxy-y-keto a, 3-unsaturated acid fragment 442 via the direct addition of a fra/i.s-vinylogous ester anion equivalent to a readily available Weinreb amide, and the facile construction of the 16-membered macrolide core of the macrosphelide series via an INOC. 

An enormous variety of olefinic types have been found to undergo such solid-state (2 + 2) photocyclodimerizations. These include cinnamic acids (128,132) derivatives of cinnamic acids such as esters (133) and amides (134) styrene derivatives (135) stilbenes (136) aliphatic mono- (137), di- (138), and triene (139) dicarboxylic acids and derivatives 1,4-diarylbutadienes (140) and their vinylogs (141), benzylidene acetones (142) and benzylidene acetophenones (143) ... 

Enamines from thioimino-esters. - Vinylogous carboxylic acid amides. Startg. thioimino-ester dissolved in triethyl phosphite, and warmed 20 hrs. at 60° under Ng -> product. 

Dicarbomethoxyacetylene has also been added to the pyrrolidine enamine derivative of acetylacetone, demonstrating a new synthesis of phthalic esters (345). A 3-acylpyridine synthesis was achieved by the addition of an acetylenic aldehyde to the vinylogous amide derived from ammonia and dihydroresorcinol (346). 

The acylation of enamines derived from cyclic ketones, which can lead to the acyl ketone or ring expansion (692-694), was studied by NMR and mass spectroscopic analysis of the products (695,696). In a comparative study of the rates of diphenylketene addition to olefins, a pronounced activation was observed in enamines (697). Enamine N- and C-acylation products were obtained from reactions of Schiff s bases (698), vinylogous urethanes (699), cyanamides (699), amides (670,700), and 2-benzylidene-3-methylbenzothiazoline (672) with acid chlorides, anhydrides, and dithio-esters (699). 

An interesting synthesis of quinolizidines was achieved using a vinylogous variation of the Bischler-Napieralski reaction. Angelastro and coworkers reported that treatment of amide 26 with PPSE (polyphosphoric acid trimethylsilyl ester) followed by reductive... 

When the enolate of an ,) - or a /j,y-unsatunited amide is used, it can react in an a or in a y fashion with a,/i-unsaturated esters, however, in most cases only a-selectivity is observed. Using l-(l-oxo-2-butenyl)pyrrolidine and lithium diisopropylamide at — 78 °C in a THF/HM-I A mixture (1 1), high. syn-selective formation of 3-alkyl-5-oxo-5-(l-pyrrolidinyl)-4-vinylpen-tanoates is achieved78,381 382. Related syn- or anti-selective additions of a vinylogous urethane also are known79. 

Besides ordinary esters (containing an a hydrogen), the reaction can also be carried out with lactones and, as in 16-38, with the y position of a,p-unsaturated esters (vinylogy). There are also cases, where the enolate anion of an amide was condensed with an aldehyde. ... 

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