Lithiation ofN-Alkyl-(o-tolyl)aziridine: Stereoselective Synthesis of Isochromans^§

Abstract

The lithiation reaction of o-tolylaziridine 1 has been investigated by using the aziridine ring capability to act as a directing metalation group. Trapped with electrophiles, the resulting o-aziridinyl benzyllithium 1-Li gives access to several functionalized aziridines 2a-j. The hydroxyalkylated derivatives 2d-j were converted into important scaffolds such as isochromans 3a-d. A stereoselective preparation of isochromans (R)-3b, (1R,3S)-3d, and (1R,3R)-3d has been developed starting from enantioenriched o-tolylaziridine.

Ring-closing metathesis as a key step to construct 2,6-dihydropyrano[2,3-c]pyrazole ring system

“…The structures of the synthesized 2-phenyl-, 2-(4-bromophenyl)-and 2-(4-fluorophenyl)-2,6-dihydropyrano[2,3-c]pyrazoles were characterized by 1 H, 13 C, 15 N and 19 F NMR spectroscopy, UV-Vis and fluorescence spectroscopy and HRMS measurements.…”

“…RCM reactions catalyzed by ruthenium alkylidene complexes 12,13 have proven to be one of the most powerful tools for the construction of nonaromatic (hetero)carbocyclic compounds [14][15][16] , in particular, oxygen heterocycles. [17][18][19] For example, treatment of 2-allyloxy-1-ethenylbenzene with Grubb's first-generation catalyst, [Cl2(PCy3)2Ru=CHPh], 20 afforded 2H-1-benzopyran in 95% yield. 21 …”

New Arylaziridinyldifluoroborates: Useful Suzuki–Miyaura Reagents

“…The solvent was removed in vacuo, and the crude product was purified by silica gel column chromatography to yield the pure product. Keywords: aziridines · C À C coupling · directed lithiation · NMR spectroscopy · organoboron reagents B NMR spectrum and two multiplets, ascribable to two diastereotopic fluorine atoms of the cyclic structure, in the 19 F NMR spectrum. The spatial relationship between groups was established by 1D NOESY experiments.…”

“…Lithiation occurred regioselectively at the lateral position [19] and subsequent reaction with BA C H T U N G T R E N N U N G (OiPr) 3 and KHF 2 gave the difluoroborate 11 exclusively in 90 % yield as a shelf-stable colorless oil that could be purified by flash chromatography. The intramolecular B-N interaction of difluoroborate 11 was established by multinuclear ( 19 F, 11 B, 13 C, 1 H) magnetic resonance analysis and 1D-NOESY experiments (see Supporting Information).…”

Palladium-Catalyzed Intramolecular Hydroarylation of 2-Bromobenzyl Propargyl Ethers: A New Access to Exocyclic Isochromans

“…The reaction appears to be general and works well regardless of the nature of the substituents on the triple bond terminus (Table 4, entries [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. The presence of a substituent at the propagylic position did not have deleterious effects on the cyclization.…”