Synthesis of 1-Aza-8-thiabicyclo[4.2.1]nona-2,4-diene 8,8-Dioxide and Its Conversion to a Strained Spirocycle via Photoinduced SO₂−N Bond Cleavage

Abstract

A route to the doubly unsaturated bridgehead sultam 12 has been developed. When irradiated at 350 nm, this conjugated diene is isomerized via a two-photon process to the structurally novel spiro heterocycle 17 constituted of cyclobutene, thietane dioxide, and pyrrolidine rings. A probable mechanism for the generation of 17 and select reactions thereof are reported. [reaction: see text]

Chemistry of Bridged Lactams and Related Heterocycles

“…438 The same ring system was found to be stable to highly oxidizing conditions with chromyl acetate, providing the α-amino acetate and the bridged keto-sultam in good selectivity (Scheme 164). 438,431 Paquette also reported the synthesis of bridged sultams containing diene motifs via bromination/olefination of the corresponding olefins under relatively harsh conditions (Scheme 165). 295,440,431,459 The diene products were later used in the photocyclization studies.…”

“…431 The proposed mechanism involves (1) homolytic cleavage of the N–SO 2 bond, (2) rebonding to give the bicyclic isomer, (3) thermally-induced [1,5]-hydrogen shift, and (4) photo-induced disrotatory closure to the cyclobutene ring. This reaction constituted the first example of a σ N–SO 2 bond cleavage in a bridged sulfonamide.…”

Novel s-tetrazine-based dyes with enhanced two-photon absorption cross-section

“…The low LUMO energy of tetrazine derivatives enables inverse demand Diels-Alder cycloaddition reactions as a heterodiene [1][2][3][4][5][6][7][8][9][10][11][12][13] and stabilizes the anionic intermediate that enables aromatic nucleophilic substitution. [14][15][16][17][18][19] Tetrazine derivatives are also used in coordination chemistry [20][21][22][23][24] because they can form complexes with electron-rich metals.…”

Formation of a Four‐Membered Ring

“…Frequently, such tricyclic compounds are intermediates in the synthesis of fenestranes.) (reaction 43) [98]. For this, the following mechanism has been discussed: the reaction starts with photochemical cleavage of the SÀN bond, followed by a radical combination to form the biradical intermediate XXXVII that in turn yields the bicyclic sulfone XXXVIII.…”