Dehydration with methanesulfonyl chloride

P-Lactams.1 /(-Amino acids are converted to /(-lactams by dehydration with methanesulfonyl chloride under phase-transfer conditions. Tetra-n-butylammonium hydrogen sulfate is the most useful ammonium salt (equation I). 

Nitrn-l-propene Preparation is accomphshed by dehydration of l-nitro-2-propanol with methanesuLfonyl chloride and triethylamine (30% ieldi, acetic... 

Nitro-l-propene Preparation is accomplished by dehydration of l-nitro-2-propanol with methanesulfonyl chloride and triethylamine (30% yield),47 acetic anhydride-AcONa (85% yield),46 or phthalic anhydride (55%)45 bp 58 °C/35 mmHg (Eq. 3.25). 

Yodav and co-workers reported that treatment of a variety of tertiary alcohols with methanesulfonyl chloride in the presence of DMAP and triethylamine produces the dehydrated products (eq 3). Acid-sensitive functionalities are not affected by the reaction conditions. 

A iD-Corticoids have been important intermediates since it was shown ° that substitution at C-9 enhances anti-inflammatory activity. These olefins are usually obtained from 11a- or 11)5-alcohols, and consequently several refined methods have been devised for effecting this dehydration. It is desirable that such methods be compatible with the presence of A" -3-ketone and 17-hydroxy functions. The first direct procedure for which high yields were claimed was described in a patent issued to Upjohn. According to this method, the alcohol (11a or )5) is treated first with A-bromoacetamide in pyridine, then with sulfur dioxide. Recently it has been claimed " that the A-haloamide/sulfur dioxide method gives results superior to other methods, although the methanesulfonyl chloride/sulfur dioxide procedure (see below) apparently was not compared (see also ref. 94). 

Attempted dehydration using an acid catalyst or iodine failed, giving mainly acetophenone. When acetic anhydride is employed instead of trlfluoroacetlc anhydride, the reaction proceeds very slowly. Dehydration with excess methanesulfonyl chloride and triethylamine gives the product in high yield however, the distilled product has a strong odor of sulfur compound. 

When methanesulfonyl chloride was allowed to react with 2,3,4,6-tetra-O-ben-zylglucopyranose and collidine in dichloromethane, the a-glucopyranosyl chloride was isolated regardless of whether the quaternary ammonium bromide was included. Addition of methanol to the reaction mixture resulted in the formation of an anomeric mixtiue of methyl glycosides. Similar results were obtained with toluenesulfonyl chloride, although it was noted that the initial sulfonylation was somewhat slower [8,9]. The use of tosyl chloride in the dehydrative coupling of alcohols with pyranoses was later revisited by Szeja and his coworkers, with the difference that aqueous... 

Methanesulfonyl chloride. 13, 176 Dehydration of allylic alcohols. hols with MsCl and EtsN (mesylationi. 10 min. 

---