Navigation

0 Hits

  • Previous / Next

You are using Science Of Synthesis as a Guest. Please login or sign up for a free trial to access the full content.
27.17.2.2.3 Method 3: N-tert-Butylhydrazones as Acyl Anion Equivalents

DOI: 10.1055/sos-SD-027-00576

Kim, S.; Yoon, J.-Y.Science of Synthesis, (200427689.

Aza anions 75, formed by the deprotonation of N-tert-butylhydrazones, react with electrophiles such as carbonyl compounds and alkyl halides at the carbon atom.[‌79‌,‌80‌] However, aza anions derived from N-phenylhydrazones react with alkyl halides principally at nitrogen.[‌81‌] Even the alkylation of aza anions obtained from N-tert-butylhydrazones 74 with alkyl halides is very sensitive to the nature of the electrophile, and both C- and N-alkylated products can form;[‌82‌] typically, iodomethane favors C-alkylation, whereas iodoethane or iodopropane give mainly N-alkylated products. When α,β-unsaturated esters and nitriles are used as electrophiles 1,4-addition can occur. The tert-butylhydrazones 74, which are unstable to chromatography and are stored in the absence of light and oxygen, have particular value in the formation of acyl anion equivalents; thus, they can be quenched at 0°C with aldehydes and ketones 76 and then protonated to afford unstable 2-(tert-butyldiazenyl)ethanols.[‌82‌] Although these products 77 revert to the parent hydrazones 74 and carbonyl compounds 76 on standing, they isomerize to hydroxyacetaldehyde tert-butylhydrazones 79 when treated with butyllithium, followed by the addition of water, via dilithium compound 78. Hydrolysis of these products to α-hydroxy ketones 80 is achieved by treatment with oxalic acid (Scheme 17). Yields are low when enolizable ketones, such as acetophenone and cyclohexanone, are used.

Meeeee 88 eeee-Meeeeeeeeeeeeee ee Meee Meeee Meeeeeeeeee[‌88‌]

Meeeeeeeeeee Meeeeeeee

8-Meeeeee-8-eeeeeeeeeeee-8-eee (88, M8=Me; M8=M; M8=Me); Meeeeee Meeeeeeee:[‌88‌]

MeMe (88.8eeee) eee eeeee eeee 8eee ee eeeeeeeeeeee eeee-eeeeeeeeeeeeee 88 (M8=Me; 8.88e, 88.8eeee) ee MMM (88eM) eeeee M8 ee 8°M. Mee eeee eee eeeeeee eee 88eee, eee eeee ee eee eeeeeeee eeee eeeeeeeeeeee (8.88e, 88.8eeee). Meeeeeeeee MeMe (88.8eeee) eee eeeee eeee 8eee, eee eee eeee eee eeeeeee eee 8e ee 8°M, eeeeee ee 88°M, eee eeee eeeeeeee eeee MeMM eee M8M (8:8, 8.8eM). Mee eeeeeee eee eeeeee ee ee, eee eeeeeee eeeeeeeeeeee, eee eee eeeeeee eeeeeeeee ee MM8Me8 (888eM) eee M8M (88eM). Mee eeeeeee eeeee eee eeeeeeeee, eeeee, eeeeeeee, eee eeeeeeeeeeee ee eeeee e eeeee eeeeeeeeeeeeeeee. Meeeee eeee (8e), M8M (88eM), eee Me8M (88eM) eeee eeeee, eee eee eeee eee eeeeeee eeeee M8 eee 88e. Me8M (888eM) eee eeeee, eee eeeeeee eee eeeee eeeeeeeee, eeeeee eeee eee. ee MeMMM8 (88eM), eeeee, eee eeeeeeeeeeee. Mee eeeeeee (8.88e) eee eeeeeeee ee eeee eee eeeee eeeeeeee; eeeee: 8.88e (88%); MM (MMMe8) ν̃eee: 8888 (MM), 8888 (M=M) ee8.

References