2-Methylsulfanylbenzo[f]isoquinoline

Abstract

S-Methylation of a 4-(naphth-2-yl)-β-thiolactam gives an intermediate 4-(naphth-2-yl) substituted 1-azetine which undergoes a [2+2] ring-opening followed by electrocyclic ring closure of the resulting 2-azadiene to give a benzo[f]isoquinoline.

Synthesis, conformation and antiproliferative activity of isothiazoloisoxazole 1,1-dioxides

“…We have shown, disappointingly, that the thiazete 1,1-dioxide (5a) is not reactive towards 1,3-dipoles or cyclopropenones, in marked contrast to the 1-azetine system, but that it does undergo rearrangement into the previously unreported 1,2,3-oxathiazolin-2-oxide (21). However, we have produced sixteen new isothiazoloisoxazoles and four new isothiazole 1,1-dioxides building upon the route used to access the thiazete 1,1-dioxide (5a).…”

“…No reactions of the imine present in the thiazete 1,1-dioxide (5a) were observed, and the starting material was returned unchanged in all cases, a huge disappointment given that we had shown that the imine within the 1-azetine system reacts easily with both nitrile oxides and cyclopropenones. [21][22][23][24] Other 1,3-dipoles (nitrile ylides, nitrilimines, nitrones, aryl azides and azomethine ylides) and dienes were found to be similarly unreactive. Interestingly, when the cyclopropenone reaction was attempted in the presence of a Lewis acid, a reaction was observed.…”

“…25 Nonetheless, we have shown that 1-azetines are able to act as precursors for the synthesis of benzoisoquinolines, 21 homotropane related heterocycles 22 and pyridines 23 via a formal [3+2]-cycloaddition reaction with cyclopropenones (which act as all-carbon 1,3-dipole equivalents) as well as acting as dipolarophiles for the synthesis of 1,2,4-oxadiazoles 24 via reaction with nitrile oxides. As a result of these successes, and given our interest in the β-sultam nucleus, we wished to explore the chemistry of the unsaturated β-sultam system, the thiazete 1,1-dioxide (4).…”

“…Our interest in four-membered ring nitrogen heterocycles has also included the study of the chemistry of the unsaturated 1-azetine (3), [21][22][23][24] a system that is easily accessed from β-lactams, although the 1-azetine remains a heterocycle that attracts very little attention. 25 Nonetheless, we have shown that 1-azetines are able to act as precursors for the synthesis of benzoisoquinolines, 21 homotropane related heterocycles 22 and pyridines 23 via a formal [3+2]-cycloaddition reaction with cyclopropenones (which act as all-carbon 1,3-dipole equivalents) as well as acting as dipolarophiles for the synthesis of 1,2,4-oxadiazoles 24 via reaction with nitrile oxides.…”

“…29 Scheme 2. Mechanism for formation of 1,2,3-oxathiazolin-2-oxide (21) Disappointed by the inert nature of thiazete 1,1-dioxide (5a) towards 1,3-dipoles and cyclopropenones, we next investigated the reactivity of isothiazole 1,1-dioxides (10a -17a) and (6a, Ar = 4-MeOC 6 H 4 , R = Et). No reactivity was observed from any of these compounds towards cyclopropenones.…”