Ketenes phenoxy

Mit einem Hydrid-OberschuB verlauft die Reduktion bis zur Alkohol-Stufe. So erhalt man aus 2,4-Dichlor-phenoxy-keten mit Lithiumalanat 85% d.Th. (2,4-Dichlor-phen-oxy)-iithanol5. 

The basic amino group of the 1-position in semicarbazide or thiosemi-carbazide may be used to react by a substitution reaction with activated halides [52], ethers [51], hydroxy [53], phenoxy [54], and amino groups [55] to yield substituted 1-semicarbazides or thiosemicarbazides. In addition, the amino group of the 1-position may add to electron-deficient double bonds [56]. Formaldehyde and other aldehydes may add to all the available free NH groups to give methylol, alkylol, or polymeric products under basic conditions [57]. Aldehydes or ketenes usually give semicarbazone derivatives, and these in turn are used analytically to identify the purity or structure of a known aldehyde [3]. 

Jarrahpour et al. [135] have described the synthesis of novel mono- and bis-spiro-[S-lactams 231 and 233, respectively, from benzylisatin 229 (Scheme 52). The starting substrate, benzylisatin 229 was prepared by reaction of isatin 228 with benzyl bromide and calcium chloride in DMF. The benzylisatin substituted imines 230 and di-imines 232 were further subjected to Staudinger reaction with ketenes derived from methoxy, phenoxy, and phthaloglycyl chlorides to afford novel mono- and bis-spiro-p-lactams 231 and 233, respectively. The configuration of benzylisatin 229 and monocyclic spiro-p-lactams 231 was established by X-ray crystallographic studies. These spiro-p-lactams will be studied as precursors of modified p-amino acids, (3-peptides and monobactam analogues. 

Solid-phase synthesis of 3,4-disubstituted (3-lactams was accomplished [104] via reaction of in situ generated ketenes with immobilized aldimines under mild conditions. Initially Fmoc-protected Wang resin strategy was followed (Scheme 15) and the [2+2] cycloaddition was performed by adding phenox-ylacetyl chloride (49, R1 = phenoxy) and triethylamine in excess to a suspension of 48 in dichloromethane. The yields ranged from good to very good for the five-step synthetic sequence and exclusive formation of the cis isomer was detected in all cases. 

Imines derived from glyoxylic acid derivatives successfully lead to 3-lactams which are potential precursors of various antibiotics (equation 29). Conjugated imines have also been used in this context they give exclusively [2 -i- 2] cycloadducts with azido-, phthalimido-, phenoxy- and vinyl-ketene precursors (equations 30 and 31). However, [4 -i- 2] adducts are the only observed products with haloketene precursors (equation 32). - ... 

This reaction was first reported by Moore in 1985. It is a synthesis of phenol (or quinone) derivatives by means of the thermal cyclization of enyne-ketenes between C2 and Cy via an aryl/phenoxy biradical intermediate. Therefore, it is generally known as the Moore cyclization. Occasionally, it is directly referred to as the Moore reaction. 

The treatment of thiazol-2-yl-N,N-dimethylimidoformamide 88 with monosubstituted ketenes such as phenyl, phenoxy, chloro, bromo, and cyano ketenes, generated, in situ, by the dropwise addition of their corresponding acid chlorides 89 in triethylamine at room temperature (Scheme 41) gave thiazolopyrimidinones 90 [66],... 

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