The Rearrangement Route to 2-Azabicyclo[2.1.1]hexanes. Solvent and Electrophile Control of Neighboring Group Participation

• Published in: Journal of organic chemistry Vol. 68; no. 13; pp. 5292 - 5299
• Main Authors: Krow, Grant R, Lin, Guoliang, Rapolu, Deepa, Fang, Yuhong, Lester, Walden S, Herzon, Seth B, Sonnet, Philip E
• Format: Journal Article
• Language: English
• Published: WASHINGTON American Chemical Society 27.06.2003; Amer Chemical Soc
• Subjects: Chemistry; Chemistry, Organic; Exact sciences and technology; Kinetics and mechanisms; Organic chemistry; Physical Sciences; Reactivity and mechanisms; Science & Technology; ASYMMETRIC-SYNTHESIS; ANALOGS; CONFORMATIONAL PROPERTIES; AMINO-ACIDS; EPIBATIDINE; 2,4-METHANOPROLINE 2-CARBOXY-2,4-METHANOPYRROLIDINE; KAITOCEPHALIN; INHIBITORS; BETA-PEPTIDES; AQUEOUS-SOLUTION; Solvent effect; Substituent effect; Organic selenide; Chemical rearrangement; Nitrogen heterocycle; Alcohol; Ester; Amine; Cyclobutane derivatives; Halogenation; Bicyclic compound; Reaction mechanism; Electrophile; Halogen Organic compounds
• ISSN: 0022-3263; 1520-6904
• DOI: 10.1021/jo034394z

The reactions of N-(alkoxycarbonyl)-2-azabicyclo[2.2.0]hex-5-enes 5 with halonium ion electrophiles were studied in polar and nonpolar aprotic solvents and also in protic media with the aim of controlling nitrogen neighboring group participation. Specifically, for bromonium ions nitrogen participation is facilitated by the polar aprotic solvent nitromethane and by the poorly nucleophilic protic solvent acetic acid. Alkene 5b and bromine/nitromethane afford only the rearranged anti,anti-5,6-dibromo-2-azabicyclo[2.1.1]hexane 6b, and NBS/acetic acid gives an 8:1 mixture favoring rearranged 5-bromo-6-acetate 6f. Conversely, pyridinium bromide perbromide/CH2Cl2 is selective for only unrearranged 5,6-dibromide 7. Iodonium and phenylselenonium ions react with alkenes 5 to give only unrearranged 1,2-addition products 9 and 10, regardless of solvent. Chloronium and fluoronium ions react with alkenes 5 to give 4-aminomethyl-3-hydroxycyclobutene 11, derived by ring cleavage.