A convenient
preparation method of N-acylbenzoxazines
has been developed, in which phenols react with nitriles and dimethyl
sulfoxide (DMSO) in the presence of a catalytic amount of (COCl)2 in CH3CN or chloroform to afford the corresponding N-acylbenzoxazines in moderate-to-good yields. DMSO acts
as a source of HCHO, which is generated in situ from the decomposition
of a methoxydimethylsulfonium salt. A regeneration cycle of the methoxydimethylsulfonium
salt is proposed, which is initiated by a catalytic amount of (COCl)2.
It has been found that the monochlorination of most of 1,3‐diketones and β‐ketoesters under investigation can be achieved using DMSO or Ph2SO/(COCl)2 at −20∼0 °C in moderate to high yields. The 1,3‐diketones, which enol forms are stabilized by an intramolecular hydrogen bond, bulky β‐ketoesters, and α‐monoalkylated 1,3‐dicarbonyls undergo chlorination well with DMSO/(COCl)2, whereas the chlorination of the less bulky β‐ketoesters needs Ph2SO/(COCl)2 instead. The chlorodimethylsulfonium salt or chlorodiphenylsulfonium salt generated by the reaction of DMSO or Ph2SO with (COCl)2 is proposed as a Cl+ source for chlorination, which provides a convenient access to the monochlorination of 1,3‐dicarbonyls.
It has been found that 2,4‐dithiapentane and dimethyl disulfide are readily prepared in useful yields from DMSO/(COCl)2 under different conditions. The reaction mixture of DMSO/(COCl)2 was treated with 1 equivalent of Et3N and 15 equivalents of H2O to afford 2,4‐dithiapentane, whereas dimethyl disulfide was obtained by the treatment DMSO/(COCl)2 with 10 equivalents of H2O without Et3N. The corresponding deuterated products, [2H8]‐2,4‐dithiapentane, [2H6]‐dimethyl disulfide, and [2H6]‐methyl methanethiosulfonate were also prepared from the reactions of [2H6]‐DMSO with (COCl)2.
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