Dimerization and Isomerization Reactions of α-Lithiated Terminal Aziridines

Allylic alcohols and amines by carbenoid eliminative cross-coupling using epoxides or aziridines

α-Lithiated terminal epoxides and N-(tert-butylsulfonyl)aziridines undergo eliminative cross-coupling with α-lithio ethers, to give convergent access to allylic alcohols and allylic amines, respectively. The process can be considered as proceeding by selective strain-relieving attack (ring-opening) of the lithiated three-membered heterocycle by the lithio ether and then selective β-elimination of lithium alkoxide.

Synthesis of Selenoaziridines: A Study on Stereochemical Outcomes of the Reaction of Aziridine Radicals and Anions Generated from Iodoaziridines

The synthesis of a new functional group in the form of selenyl-substituted aziridines is described. Selenoaziridines are stereoselectively prepared by functionalization of intact aziridine precursors involving radical and anionic intermediates. Radicals are generated from cis-N-Ts iodoaziridines by activation of the C-I bond using alkoxides as a source of single electrons. These form predominantly trans-substituted selenoaziridines dependent on the size of the diselenide. cis-Aziridinyllithiums generated by Li-I exchange also react with diselenides stereospecifically to form a range of cis-selenoaziridines. Proposals for the stereochemical outcome are presented.

Generation and electrophile trapping of N-Boc-2-lithio-2-azetine: synthesis of 2-substituted 2-azetines

s-BuLi-induced α-lithiation–elimination of LiOMe from N-Boc-3-methoxyazetidine and further in situ α-lithiation generates N-Boc-2-lithio-2-azetine which can be trapped with electrophiles, either directly (carbonyl or heteroatom electrophiles) or after transmetalation to copper (allowing allylations and propargylations), providing a concise access to 2-substituted 2-azetines.

Synthesis of cis-C-iodo-N-tosyl-aziridines using diiodomethyllithium: reaction optimization, product scope and stability, and a protocol for selection of stationary phase for chromatography

The preparation of C-iodo-N-Ts-aziridines with excellent cis-diastereoselectivity has been achieved in high yields by the addition of diiodomethyllithium to N-tosylimines and N-tosylimine-HSO2Tol adducts. This addition-cyclization protocol successfully provided a wide range of cis-iodoaziridines, including the first examples of alkyl-substituted iodoaziridines, with the reaction tolerating both aryl imines and alkyl imines. An ortho-chlorophenyl imine afforded a β-amino gem-diiodide under the optimized reaction conditions due to a postulated coordinated intermediate preventing cyclization. An effective protocol to assess the stability of the sensitive iodoaziridine functional group to chromatography was also developed. As a result of the judicious choice of stationary phase, the iodoaziridines could be purified by column chromatography; the use of deactivated basic alumina (activity IV) afforded high yield and purity. Rearrangements of electron-rich aryl-iodoaziridines have been promoted, selectively affording either novel α-iodo-N-Ts-imines or α-iodo-aldehydes in high yield.

Highly cis-selective synthesis of iodo-aziridines using diiodomethyllithium and in situ generated N-Boc-imines

The first preparation of iodoaziridines is described. The addition of diiodomethyllithium to N-Boc-imines affords these novel aziridines in high yields. The reaction proceeds in one-pot via a highly diastereoselective cyclisation of an amino gem-diiodide intermediate.

Stille coupling of an aziridinyl stannatrane

An aziridinyl stannatrane 8 couples with aryl or alkenyl halides RX under modified Stille conditions to afford substituted aziridines. Efficient coupling at room temperature is possible in the best examples in the presence of ((t)Bu3P)2Pd and CuOP(O)Ph2 (CuDPP).

Metalated aziridines for cross-coupling with aryl and alkenyl halides via palladium catalysis

The palladium-catalyzed coupling of an aziridinylzinc chloride intermediate with alkenyl and aryl halides has been demonstrated. The method provides products with retention of aziridine stereochemistry. The utility of the coupling procedure is illustrated in the synthesis of structures related to l-furanomycin.

α,β-Aziridinylphosphonates by lithium amide-induced phosphonyl migration from nitrogen to carbon in terminal aziridines

N-Phosphonate terminal aziridines undergo lithium 2,2,6,6-tetramethylpiperidide-induced N- to C-[1,2]-anionic phosphonyl group migration under experimentally straightforward conditions, to provide a stereocontrolled access to synthetically valuable trans-α,β-aziridinylphosphonates. The utility of this chemistry has been demonstrated in the asymmetric synthesis of a β-aminophosphonate.

Lithiation-electrophilic substitution of N-thiopivaloylazetidine

The fourth protocol: the rarely studied N-thiopivaloyl group plays a crucial role in mediating efficient α lithiation and incorporation of diverse electrophiles onto an azetidine ring; in the presence of chiral ligands, this chemistry also provides the first example of an enantioselective electrophilic substitution on a four-membered ring.

Terminal aziridines by alpha-deprotonation/electrophile trapping of N-protected aziridine

N-tert-Butylsulfonyl and N-tert-butylsulfinyl aziridine undergo alpha-lithiation/electrophile trapping providing a new entry to terminal aziridines. With N-tert-butylsulfinyl aziridine complete asymmetric induction is observed alpha to nitrogen.