Reactions of Pyridine Analogues of Aza-ortho-xylylenes Generated from 1,3-Dialkylpyridosultams

Aza-ortho-xylylenes in Organic Synthesis

“…[48] Similarly, isothiazolo[4,3-b]pyridine 2,2-dioxide (51) can be obtained from 2-chloro-3-(sulfonylamino)pyridine (50). [50,51] An aryne-mediated intramolecular substitution in 2-chloro-N-methyl-N-methanesulfonylaniline (52) [52,53] and (2-bromophenyl)methanesulfonamide (57) [54] results in The simplest benzosultam (59) can also be obtained upon treatment of sodium (2-aminophenyl)methanesulfonate (55) with POCl 3 (36% yield) [55] or by cyclization of (2-chlorophenyl)methanesulfonamide (56) in the presence of K 2 CO 3 and copper bronze (62% yield), [55] as shown in Scheme 14.…”

“…Further functionalization of the obtained N-alkyl-benzosultams by alkylation (Scheme 11), [51,56,57] nitroarylation, [49,51,56,58] and Knoevenagel condensation with aldehydes [56,59] provides the 3-substituted benzosultams.…”

“…[67] Aza-ortho-xylylenes generated from 3-alkylbenzosultams do not enter into [4ϩ2] cycloadditions, but instead undergo [1,5]-sigmatropic hydrogen shifts to produce 2-vinylaniline derivatives. [51,57,71,72] This occurs even when aza-ortho-xylylenes are generated from 3-alkylbenzosultams bearing an alkyl chain with a terminal double bond suitable for intramolecular [4ϩ2] cycloaddition, such as in 98, which yields (via 99) the aniline derivative 101 and not the cycloadduct 102 (Scheme 25). [ 3-Amino-2-(cyclohepten-1-yl)pyridine (105) is formed in good yield as a result of a [1,5]-hydrogen shift in the diazaxylylene 104, generated from 3,3-hexamethylenepyridosultam (103) (Scheme 26).…”

“…[ 3-Amino-2-(cyclohepten-1-yl)pyridine (105) is formed in good yield as a result of a [1,5]-hydrogen shift in the diazaxylylene 104, generated from 3,3-hexamethylenepyridosultam (103) (Scheme 26). [51] Analogous cyclopentene and cyclohexene derivatives are also available. [51] Scheme 26…”

“…[72] The pyridine analogue of 106 gives the corresponding 2-(2-pyridyl)indene. [51] Scheme 27 A cascade of pericyclic transformations initiated by the thermal extrusion of SO 2 from 3,3-trimethylenebenzosultams such as 109 [57] and its pyridine analogue [51] can be classified as domino reactions. [73] A [1,5]-hydrogen shift in the xylylene 110 produces the cyclobutene derivative 111, which, under the reaction conditions used, undergoes an electrocyclic opening of the four-membered ring to form the isolable 2-arylbuta-1,3-diene (112).…”