A Lewis Acid Catalyzed Intramolecular [4+3] Cycloaddition Route to Polycyclic Systems That Contain a Seven‐Membered Ring

Abstract

Two simple steps, including a new intramolecular [4+3] cycloaddition, are required for the preparation of polycycles that contain a seven‐membered ring from 2‐methyleneaziridines (see scheme). The diene component is introduced by selective lithiation/alkylation at C3 of the aziridine ring. Lewis acid catalyzed cyclization leads to the products in good yields with stereocontrol.

An unusual methylene aziridine refined inP21/cand the nonstandard settingP21/n

“…The title compound, 6-tert-butyl-3-oxa-2-thia-1-azabicyclo-[5.1.0]oct-6-ene 2,2-dioxide, (1), and related methylene aziridines (Feast et al 2009) were prepared during our ongoing study of nitrogen-containing 1,3-dipoles (Robertson et al, 2005;White, 2007) in order to probe their potential as 2-aminoallyl cation precursors (Prié et al, 2004).…”

Methyleneaziridines: Unusual Vehicles for Organic Synthesis

“…Both produce 87 and 88 but the relative amounts of these two diastereomers is dependent on the alkene geometry in the starting material (Scheme 24). 28 We rationalise this stereochemical outcome by proposing that cycloadditions proceed via compact transition states, with the tethering arm orientating itself anti-to the bulky Lewis acid complexed amino substituent. Thus, the conversion of (Z)-and (E)-86 into the major products 87 and 88 proceeds via 89 and 90, respectively (Scheme 24).…”

“…10 As 22 is readily made by the addition of dibromocarbene to the corresponding alkene, this route is convenient for the synthesis of a number of gem-disubstituted precursors. 22,25,27,28 (R = CPh 3 , R 1 , R 2 = H) by reacting amine 23 with trityl chloride. 6 Despite the harsh reaction conditions employed in the cyclization, many functional groups survive unscathed (Figure 2).…”

Synthesis and applications of methyleneaziridines

“…In this case, the reaction characteristic of bicyclic MAs was analogous to monocyclic MAs, as reported by Shipman. 61 The examples of intermolecular [4 + 3] reactions were reported by the Schomaker group. 84 Based on their previous research on bicyclic MAs, a tandem allene aziridination/[4 + 3]/ reduction sequence was skillfully designed and successfully utilized to convert homoallenic sulfamates into densely functionalized aminated cycloheptenes.…”