Rearrangements of Allene Oxide, Oxyallyl, and Cyclopropanone

Abstract

A detailed theoretical study of the rearrangement of allene oxide to cyclopropanone and the racemization of substituted cyclopropanones and the isomerization of substituted cyclopropanones is presented. The rearrangement of allene oxide to cyclopropanone was found to proceed in a stepwise fashion in which allene oxide first undergoes conversion to oxyallyl via a newly found transition structure with subsequent ring closure of the oxyallyl to cyclopropanone. It is shown that a previously found transition structure is on the pathway that results in the racemization of chiral-substituted cyclopropanones. A new transition structure was also located that accounts for the previously observed conversion of cis-2,3-di-tert-butylcyclopropanone to its trans diastereomer. The discussion is based on the results of DFT and CASSCF methods. IRC calculations were carried out for all transition structures located. Single-point energies were calculated with the CASPT2N, QCISD(T), and UQCISD(T) methods. Good agreement was found between the calculated results and those available from experiment.

Novel Allene Oxide Synthase Products Formed via Favorskii‐Type Rearrangement: Mechanistic Implications for 12‐Oxo‐10,15‐phytodienoic Acid Biosynthesis

“…[10,11] Neither cyclopropanones nor their degradation products have been detected as AOS-reaction intermediates before. Moreover, our results show that not all hydroperoxides form Favorskii products (and thus cyclopropanones) via allene oxides.…”

“…Conversion of 9-HPOD by LeAOS3 resulted in the expected formation of 10-oxo-PDA along with a-ketol, and no Favorskii product was detected (Table 2, line 9). With all three enzymes (LeAOS3, flax seed AOS and ZmAOS), g-9-HPOT produced nearly identical oxylipin profiles: the Favorskii product 3 was detectable along with the major products, a-ketol and 10-oxo-PDA (Table 2, rows [10][11][12].…”

“…[7][8][9] Moreover, as known from organic chemistry, allene oxides coexist with two valence tautomers: the oxyallyl zwitterion and cyclopropanone. [10,11] There is no experimental evidence for the existence of cyclopropanone fatty acids as AOS products or intermediates; some mechanistic details of allene oxide conversions still have to be uncovered.…”

Photoelectron Spectroscopic Study of the Oxyallyl Diradical

“…23,28,30 Electronic structure calculations find quite flat potential energy surfaces for the 1 A 1 states of both TMM and OXA along the corresponding coordinates of three-membered-ring formation. 17,23,24 In particular, the photoelectron spectrum of the OXA radical anion shows broad line widths for the vibronic Figure 12. Schematic representation of the principal electronic configurations of TMM (left), OXA (right), and their corresponding radical anions.…”

Cyclization Cascade of Allenyl Azides: A Dual Mechanism

“…The choice of DFT and the Pople basis sets is backed by earlier studies in which this method offered reasonable results at a moderate cost despite the presence of diradical species in the reaction profile. [10][11][12] Due to the potential diradical character of some of the structures considered in this work, the internal and external stability of the wavefunctions was computed via the Hermitian stability matrices A and B in all cases. 13 For all the structures exhibiting unstable restricted wavefunctions, the spin-symmetry constraint of the wavefunction was released (i.e.…”