Cycloadditions in syntheses. XXXV. 2-Cyano-1,2-dihydrocyclobuta[a]naphthalene and its derivatives: synthesis and reaction with olefins.

Cyclobutarenes and Related Compounds

“…The endo isomer 113 is more stable, and upon base-catalyzed equilibration, it predominates (9:1). Treatment of either isomer with t -BuOK in t -BuOH at 80 °C affords the carboxamide 114 in 22% yield. 83a,b When the adducts are refluxed with t -BuOK in dry benzene, the formation of 115 (48%) along with 114 (35%) is observed (Scheme ) 28 …”

“…83a,b When the adducts are refluxed with t-BuOK in dry benzene, the formation of 115 (48%) along with 114 (35%) is observed (Scheme 28). 84 Kaneko et al have used the same approach for the synthesis of 92 from 116 and 118 from 117 (Scheme 29). [85][86][87] 2,3-Dichlorobenzo[b]thiophene (119) undergoes photocycloaddition with vinyl bromide in a benzophenone-sensitized reaction.…”

“…Cyclobutarenes undergo bacterial oxidation, preferentially at the benzylic position, to give monooxygenated products. For example, naphthalene dioxygenase-catalyzed oxidation of 1 in intact cells of Pseudomonas fluorescens 127-68 XVII yielded exclusively the benzylic oxidation products, benzocyclobutenol (105a) and cyclobutarenone (84). Cyclobutarenone ( 84) is presumed to result from the action of alcohol dehydrogenase on 105a.…”

The Diels–Alder Reaction in Steroid Synthesis

“…Nevertheless, this type of IMDA reaction has been used several times in the synthesis of steroids and analogues. [143][144][145][146][147]…”

Fe(III)-Catalyzed Bicyclization of Yne-Allenones With Indoles for the Atom-Economic Synthesis of 3-Indolyl Cyclobutarenes

“…Due to the thermodynamic stability associated with the aromatic system and the kinetic reactivity of the strained cyclobutene ring (Cava and Napier, 1956; Mehta and Kotha, 2001), these molecules behave as reliable and synthetically useful feedstocks (Christophe et al, 1998) and have been extensively applied in natural product syntheses (Funk and Vollhardt, 1977, 1979; Grieco et al, 1980; Taber et al, 1987; Nemoto et al, 1995; Michellys et al, 2001). With these contributions in mind, great efforts to establish synthetic protocols for cyclobutarene synthesis have been developed which include 1,4-elimination-cycloaddition of functionalized arenes (Gray et al, 1978; Schirch et al, 1979; Sekine et al, 1979; Lenihan and Shechter, 1994, 1998; Chou et al, 1995), Parham cyclization (Bradsher and Hunt, 1981; Buchwald et al, 1987a,b; Beak and Selling, 1989; Aidhen and Ahuja, 1992), photo-induced cycloadditions (Parham et al, 1976; Kaneko and Naito, 1979; Neckers and Wagenaar, 1981; Kaneko et al, 1982; Kanao et al, 1983; Sato et al, 1987; Hoffmann and Pete, 1996), thermal extrusion reactions (Toda et al, 1988; D'Andrea et al, 1990; Hickman et al, 1991; Shimada et al, 1993; Andersen et al, 1996; Craig et al, 1998), intramolecular addition of carbanions to benzynes (Bunnett and Skorcz, 1962; Krohn et al, 1978; Gowland and Durst, 1979), [2 + 2 + 2] cycloadditions of 1,5-hexadiyne (Peter and Vollhardt, 1977, 1984; Funk and Vollhardt, 1980; McNichols and Stang, 1992), ring expansion of cycloproparenes (Birch et al, 1964; Iskander and Stansfield, 1965; Buckland et al, 1987; Kagabu and Saito, 1988; Müller et al, 1989), and [2 + 2] cycloadditions of allene precursors (Inanaga et al, 1992; Ezcurra and Moore, 1993; Toda et al, 1994) and other methods (Markgraf et al, 1969; Garratt and Nicolaides, 1972, 1974; Bilyard et al, 1979; Warrener et al, 1993). However, these methods encounter some drawbacks such as high temperatures (400°C-800°C), strong bases ( n -BuLi and NaNH 2 ), multiple steps, or a narrow substrate range.…”