1.1- Enediamines cycloaddition

Dimethyl acetylenedicarboxylate (80) undergoes initial 1,2 cycloaddition with acyclic enamines to form cyclobutene intermediates which immediately decompose into acyclic dienaminodiesters (94,95). When an acyclic n/c-enediamine is used instead of a simple acyclic enamine, a dienediamino-diester is produced via a cyclobutene intermediate (95a). A cyclization reaction of dimethyl acetylenedicarboxylate with an acyclic enaminoketone... 

Cumulenes such as butatrienes and hexapentaenes can undergo cycloaddition at several possible double-bond sites. The electrophilic l,l-diphenyl-4,4-bis(trifluoromethy )butatriene (34), however, reacts with ketene acetals and geminal enediamines at the central double bond exclusively.25 In the case of the ketene acetal cycloadduct 35 (R1 = H R2 = R3 = OMe). acid-catalyzed hydrolysis gives the cyclobutanone. 

Different modes of reaction are known for the reaction of 1,1-enediamines with electrophilic acetylenes. Simple 1,1-enediamines undergo cycloaddition reaction which will be discussed in Section V.A119, whereas conjugated 1,1-enediamines act as nucleophiles towards activated acetylenes. 

Simple 1,1-enediamines react with diethyl azodicarboylate (182, R = Et) to give mainly, after hydrolysis, A/,7V -dicarboethoxyhydrazinylamides (183) in low to moderate yields (equation 74). A small amount (6%) of [2 + 4] cycloaddition product was also isolated in the case of 1,1-dipiperidinylethylene 35 (X = CH2)146. Secondary cyclic 1,1-enediamines 8, 75a and 77 react with diethyl azodicarboxyiate smoothly at room temperature to afford excellent yield of C-adducts 18429,39. 1,1-Enediamines 185 also led to adduct 17 or 17 when refluxed with 182 in methylene chloride (Scheme 10)37 147 see section h a for tautomerization between 17, and 17 ). An ene-addition... 

In this section, we will discuss the few, but interesting, cycloaddition reactions156 of 1,1-enediamines. These cycloadditions provide a useful synthetic approach to a variety of complex compounds, and reflect the differences between 1,1-enediamines and en-amines on the one hand, and between simple and conjugated 1,1-enediamines on the other. 

A [2 + 2] cycloaddition reaction between simple 1,1-enediamine and a sulfonyl chloride was also observed157-159. In the presence of a base, 1,1-dimorpholinoethy-lene (154) reacted with methanesulfonyl chloride (199) in ether or in tetrahydrofuran to give 3-morpholinothietane 1,1-dioxide (200) in good yield (equation 83). However, the reaction takes a different course in chloroform, leading to the conjugated 1,1-enediamine 201. Other reactants than 154 and 199 did not form cycloaddition products under the same conditions160. 

Simple 1,1-enediamines act as electron-rich olefins in undergoing inverse electron demand Diels-Alder reactions with dienes. Efforts have been focused on their cycloaddition reactions with heterocyclic azadienes161,162. For example, 1,1-enediamines 35 and 154 react easily with 5-nitropyrimidine to give the pyridine derivatives 203 via the 1,4-addition intermediates 202 (equation 84)163. 

The only 1,1-enediamines known to react with acyclic dienes in an all-carbon [2 + 4]-cycloaddition are the alkylideneimidazolidines, as has been reported by Heuschmann and Gruseck165,166 in recent years. Thus, cycloaddition products are formed at or below room temperature when 3 is treated with 2,4-dienoates. Hydrolysis of cycloadducts 212 by dilute acid leads to 2-cyclohexenone derivatives 215 or their enol tautomers 216 via 213 and 214 (Scheme 11). The reaction has been extended to... 

In contrast to the cycloaddition of simple 1,1-enediamines, the reaction between conjugated 1,1-enediamines and nitrile oxides proceeds at a slower rate and the yields of products 222 are low (equation 92)172,173. 

The reaction of cyclic 1,1-enediamines 7 and 8 with azides appears interesting. Nitro-substituted 1,1-enediamines 7 reacted with benzenesulfonyl azide to give triazoles 225 in moderate yields. Other secondary 1,1-enediamines analogues gave similar products in comparable yields. The reaction has been postulated to proceed by a sequence of 1,3-cycloaddition to 223, a Dimroth rearrangement to 224 and deamination to 225 (Scheme 12)174. Junjappa and coworkers175 have reported that 1,1-enediamines... 

In contrast to benzenesulfonyl azide, the reaction between 8 and aryl azides gives only a small amount of 226. Instead, highly substituted triazoles 228 are formed as the major products176,177. When 4-nitrophenyl azide is used, the reaction furnishes 228 exclusively. It has been believed that the reaction involves two competitive pathways and benzoyl-substituted 1,1-enediamines 8 act mainly as nucleophiles rather than as 1,3-dipolarophiles toward aryl azides. Consequently, they add to the azide group and, following intramolecular cyclocondensation, give products 228. Only in the case of unfavorable electronic factors does 1,3-cycloaddition reaction to give 226 take place (Scheme 13)177. 

Simple 1,1-enediamines react with diethyl azodicarboylate (182, R = Et) to give mainly, after hydrolysis, N.A -dicarbocthoxyhydrazinylamidcs (183) in low to moderate yields (equation 74). A small amount (6%) of [2 + 4] cycloaddition product was also isolated in the case of 1,1-dipiperidinylethylene 35 (X = Secondary... 

A [2 -f 2] cycloaddition reaction between simple 1,1-enediamine and a sulfonyl chloride was also observed In the presence of a base, 1,1-dimorpholinoethy-... 

Simple 1,1-enediamines undergo 1,3-dipolar cycloaddition readily with 1,3-dipolar reagents. The 1,3-cycloadducts, which are stable and have been isolated in some cases, undergo further deamination by heating or in the presence of acid to give heteroaromatic products. This behavior resembles that of the parent enamines . Thus, 1,1-enediamines react with azides - and nitrile imines smoothly to give high yields of the cycloaddition products 217 and 219, and triazoles 218 and pyrazoles 220 after deamination (equations 89 and 90). 

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