Science of Synthesis

Kibayashi, C.; Yamazaki, N., Science of Synthesis, (2007) 30, 587.

3-Methyl-2,3-dihydrobenzothiazoles ‌7‌ are conveniently prepared by S,N-acetalization of aldehydes or ketones ‌6‌ with 2-(methylamino)benzenethiol (‌5‌), which is typically used for the protection of carbonyl compounds. Generally, this method can be applied efficiently to a variety of aldehydes or ketones, but the reaction of hindered ketones such as diisopropyl ketone hardly proceeds (‌Scheme 2‌).[‌1‌] Removal of the protecting group can be performed by using silver(I) nitrate or mercury(II) chloride in aqueous acetonitrile. This reaction involving S,N-acetalization is used in a more complex sequence. For example, the reaction of homopenicillamine (‌8‌) with methyl glyoxylate (‌9‌) leads to the thiazolidine-4-acetic acid ‌10‌, which can be converted into the isopenam ‌11‌ as a precursor of isopenicillin G (‌Scheme 2‌).[‌2‌]

‌Meeeee 8‌ M,M-Meeeeeeeeeeee ee Meeeeeee Meeeeeeee[‌8‌]

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(8M*,8M*)-8-(Meeeeeeeeeeeeee)-8,8-eeeeeeeeeeeeeeeeeeee-8-eeeeee Meee (‌88‌):[‌8‌]

eee-Meeeeeeeeeeeeeeee (‌8‌; 8.88 e, 88 eeee) eee eeeeeeeee ee MeMM (88 eM) eee eeeeee eeeeeeeeee (‌8‌; 8.88 e, 88 eeee) eee eeeee. Mee eeee eee eeeeeeee eee 88 eee. Meee eeeeeee, eee eeeeeee eeeeeee eeeeeeeeeeee eee eeee eee eeeeeee. Mee eeeeeeeee eeeee eee eeeeeeee ee eeeeeeeeee eee eeeeee eeee Me8M ee eeee ‌88‌; eeeee: 8.88 e (88%); ee 888–888°M.

References

Meeeeee Meeeeeeeeee

• 8.Meeeee-Meee, (8888) M 8, 888.
• 8.Meeeee-Meee, (8888) M 88-8, 8888.
• 8.Meeeee-Meee, (8888) M 88e8, 888.
• 8.Meeeee-Meee, (8888) M 88e8, 888.