Synthesis of functionalised azepanes and piperidines from bicyclic halogenated aminocyclopropane derivatives

Abstract

A series of 6,6-dihalo-2-azabicyclo[3.1.0]hexane and 7,7-dihalo-2-azabicyclo[4.1.0]heptane compounds were prepared by the reaction of dihalocarbene species with N-Boc-2,3-dihydro-1H-pyrroles or -1,2,3,4-tetrahydropyridines. Monochloro substrates were synthesised as well, using a chlorine-to-lithium exchange reaction. The behaviour of several aldehydes and ketones under reductive amination conditions with deprotected halogenated secondary cyclopropylamines was investigated, showing that this transformation typically triggers cyclopropane ring cleavage to give access to interesting nitrogen-containing ring-expanded products.

Photochemical Deracemization of Allenes and Subsequent Chirality Transfer

“…Eventually, it was found that compound 1 a was most reliably protected by complete deprotonation of the lactam and subsequent treatment with di‐ tert ‐butyl dicarbonate (Boc 2 O). The N ‐Boc protected lactam 8 was expected to be susceptible to a ring opening reaction by nucleophiles . As an example, we employed phenyl magnesium bromide as a potential reagent which indeed led to a smooth conversion.…”

Practical and Modular Construction of C(sp3)-Rich Alkyl Boron Compounds

“…The ability to access such an alkyl boron reagent would provide a powerful functional handle, allowing for a myriad of downstream functionalizations, including single-and two-electron transfer pathways, and 1, 2-metallate rearrangements [8][9][10] . To this end, radical precursors (such as halides, pseudo-halides, redoxactive esters) 11,12 , olefins, ate complexes 13 , organolithium reagents 14 , and stable diazo compounds 15,16 have been demonstrated as powerful precursors to such alkyl boron species (Figure 1B). However, these approaches towards alkyl boron compounds are either non-modular and/or require air-and moisture sensitive organometallic reagents or potentially explosive diazo compounds.…”

Radical Cyclization of Ynamides to Nitrogen Heterocycles

“…20 Finally, the double bond in 8a could also be smoothly and stereospecifically dichlorocyclopropanated to spirocyclic pyrrolidine 26 with chloroform and sodium hydroxide under phase-transfer conditions. 21,22 Scheme 3 Chemical diversification of representative 2-benzylidene nitrogencontaining heterocycles.…”