A 3,3-sigmatropic rearrangement in the M+· of phenyl allenylmethyl ether is proposed for the observed losses of CO, C2H4, and ĊH3. Direct cyclization in the M+· also leads to the [M — CH3] ion. The presence of sulfur as the heteroatom in phenyl allenylmethyl sulfide does not significantly influence the occurrence of Claisen rearrangement. Ortho interaction of the nitro group with the allenyl double bond in the side chain leads to characteristic fragment ions in 2-nitrophenyl allenylmethyl ether. Linked scans, high-resolution mass spectrometry, collision-activated dissociation—B/E linked-scan spectra, and D-labeling have been employed to support the proposed mechanisms and ion structures. © 1995, American Society for Mass Spectrometry. All rights reserved.

Kalapattukuppuswamy Kuppuswamy B. Balasubramanian

Tiruvenkatanathapuram R. Balasubramanian

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IIT Madras

Electron-impact-induced 3,3-sigmatropic rearrangement and cyclization in phenyl allenylmethyl ethers

Journal of the American Society for Mass Spectrometry

Authors group

Hari Balasubramanian

Indian Journal of Pharmacology

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Sulfur Reagents in Organic Synthesis

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Journal of the Chemical Society, Perkin Transactions 2

Claisen rearrangements and cyclisations in phenyl propargyl ethers under electron impact conditions

Phenyl allenyl ethers undergo Claisen rearrangement under electron impact conditions producing intense [M  CO] ions. Another competing fragmentation pathway in these compounds is an intramolecular aromatic substitution followed by the loss of H˙ or the substituent to give rise to fragments corresponding to benzopyrilium cations. Electron‐withdrawing substituents on the phenyl ring favour the cyclization reaction. An interesting ortho interaction of the nitro group with the allenic moiety leads to the expulsion of CO2 from the molecular ion. The proposed fragmentation pathways and the ion structures are established with the help of linked‐scan spectra (B/E, B2/E), collision activation decomposition spectra and high‐resolution data. Copyright © 1992 John Wiley &amp; Sons, Ltd.

Organic Mass Spectrometry

Claisen rearrangement in phenyl allenyl ethers on electron impact

Journal	Journal of the American Society for Mass Spectrometry
ISSN	10440305
Open Access	Yes