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Ring Opening of 2,5-didehydrothiophene: Matrix Photochemistry of C4H2S Isomers

Ring Opening of 2,5-didehydrothiophene: Matrix Photochemistry of C4H2S Isomers

Yong Seol Kim, Hiroshi Inui, Robert J McMahon

J Org Chem. 2006 Dec 22;71(26):9602-8.

PMID: 17168576

Abstract:

Irradiation (lambda > 254 nm) of matrix-isolated 2,5-diiodothiophene (10) gives rise to IR bands assigned to ethynylthioketene (6). Diethynyl sulfide (3), which would form in the process of retro-Bergman cyclization of the incipient 2,5-didehydrothiophene (4), is not detected. Under the same irradiation conditions, matrix-isolated diethynyl sulfide (3) rearranges to thioketene 6 and butatrienethione (5), the global minimum on C4H2S potential energy surface. The photochemical formation of thioketene 6 from either diyl 4 or sulfide 3 may be interpreted in line with a recent computational prediction on the thermal ring opening of diyl 4, which favors C-S bond cleavage, leading to 6, over C-C bond cleavage, leading to 3. Photolysis of matrix-isolated 3,4-thiophenedicarboxylic acid anhydride (11) enables the observation of the photoequilibration of three low-energy C4H2S isomers, butatrienethione (5), ethynylthioketene (6), and butadiynylthiol (7), via apparent [1,3]-hydrogen shifts.

Chemicals Related in the Paper:

Catalog Number	Product Name	Structure	CAS Number	Price
AP4282295	3,4-Thiophenedicarboxylic acid		4282-29-5	Price

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