Ethyl propiolate, amine addition

The ene addition of ethyl propiolate to P-pinene is catalysed by aluminium chloride as expected, the reaction is stereospecific and affords (545) in 82 % yield after 2 days at room temperature in benzene solution. Other 1,1-dialkylethylenes reacted similarly, but 1,2-dialkyl- and monosubstituted ethylenes, however, afforded products of stereospecific [2 +2] addition presumably short-lived dipolar intermediates are formed in the non-ene processes. Reaction of selenium tetrachloride with two equivalents of t-butylamine or toluene-p-sulphonamide in dichloromethane in the presence of four equivalents of an amine base produces solutions thought to contain iminoselenium compounds RN=Se=NR (R = Bu or Ts). Both compounds reacted with P-pinene to afford the allylic amination products (546). An even more... 

Kinetic studies of Michael addition of alicyclic secondary amines to ethyl propiolate in H2O and MeCN have demonstrated a substantial solvent effect on reactivity and transition-state structure. The amines were found to be less reactive in MeCN, although they are by 7-9 units more basic in the aprotic solvent. The reaction rates for morpholine and deuterated morpholine proved to be identical, which rules out both a stepwise mechanism in which proton transfer would occur in the RLS and a concerted mechanism in which nucleophilic attack and proton transfer would occur through a four-membered cyclic transition state. Consequently, a stepwise mechanism with proton transfer occurring after the RLS is probable. Br0nsted-type plots were found to be linear with = 0.29 and 0.51 in H2O and MeCN, respectively, indicating that bond formation is not advanced significantly in the RLS. The small value is also consistent with the absence of isotope effect. ... 

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