Synthetic and mechanistic studies of the retro-Claisen rearrangement. 2. A facile route to medium-ring heterocycles via rearrangement of vinylcyclopropane- and cyclobutanecarboxaldehydes

One‐Pot Synthesis of Metastable 2,5‐Dihydrooxepines through Retro‐Claisen Rearrangements: Method and Applications

“…The computational studies support the experimental resultsa nd can explain the reactivity differenceo bserved between substrates derived from cyclic or linear 1,3-diketones.T his study thus complementst he chapter on this powerful rearrangement discovered in the 1960s. [1][2][3][4][5][6] Importantly,t his one-pot retro-Claisen rearrangement was applied to the total synthesis of the natural product radulanin A. Its phytotoxic properties were demonstrated for the first time validating our allelopathich ypothesis and paving the way to the development of natural herbicides, which may have better environmental profiles than those currently used.…”

The Divergent Synthesis of Nitrogen Heterocycles by Rhodium(II)‐Catalyzed Cycloadditions of 1‐Sulfonyl 1,2,3‐Triazoles with 1,3‐Dienes

“…The above outcomes provide information on the plausible mechanism of the described cycloadditions, as rationalized in Scheme 6. Thus, the rhodium(II) iminocarbene A first reacts with the 1,3-diene B to yield cyclopropylaldimine intermediate C, which then advances to D by a aza-Cope rearrangement [20] (path a) and/or E by a cyclopropylimine rearrangement [21] (path b). While a full account of the effect of substitution pattern and geometry of 1,3-diene partners on the reactions remains to be achieved, it seems that the reactions with 1-aryl-and 2-aryl-1,3-dienes mainly follow path a to afford D. Notably, for 1-aryl-1,3-dienes, the resulting D (R = 2-Ar, Scheme 6) could readily undergo allylic amine 1,3-migration to evolve into E (e.g.…”

Stereoselective Lewis Acid Mediated [1,3] Ring Contraction of 2,5‐Dihydrooxepins as a Route to Polysubstituted Cyclopentenes

“…[8,9] An equilibrium between 1 and 2 has been predicted computationally, [10] and may be shifted towards the 2,5-dihydrooxepin with p-stabilizing substituents [Eq. (2); EDG = electrondonating group, EWG = electron-withdrawing group].…”

“…(2); EDG = electrondonating group, EWG = electron-withdrawing group]. [9] We began our investigations by developing a highly modular approach to the 2,5-dihydrooxepin skeleton. A representative synthesis is illustrated in Scheme 1.…”