Amidine function in constructing novel types of phosphorus-containing heterocycles

Novel Approaches to Fused Phospha-Pyrimidines

“…Then treatment of 2 with saturated ammonium solution in dichloromethane afforded iminophosphonate 3, which spontaneously cyclized to diazaphosphinine 4. 6 Scheme 2 Reagents and conditions: (i) PCl 3 , py, r.t., 1.5 h; (ii) amine, Et 3 N, PhH, 1.5 h; (iii) C 2 Cl 6 , PhH; (iv) NH 3 , CH 2 Cl 2 , 24 h.…”

Heterocyclisation of trisubstituted formamidines containing an aryl or hetaryl substituent at the imine nitrogen atom

“…76,77 For example, the phosphorus salts 87 cyclise on treatment with ammonia to yield 3-methyl-4,4-bis(amino)-1-phenylpyrazolo[4,5-e]-1,3,4l 5 -diazaphosphinines 88 via intermediate iminophosphonic diamides 89. 78 When the amidine molecule incorporates two different reaction sites which occupy positions neighbouring the amidine group, the more reactive site participates predominantly in the cyclisation. For instance, N 1 ,N 1 -dimethyl-N 2 -(1-methoxy-7,8-dimethyl-4-oxo-6-cyanoisochroman-5-yl)formamidine 90 is converted into 6-methoxy-7,8-dimethyl-4H,6H-5-oxa-1,3-diazaphenalene-9-carbonitrile 91, the cyano group remaining intact during the reaction.…”

Phosphorylation of Arylureas and Arylcarbamates: A New Prospect

“…18 Like N,N-diarylureas, ureas 13, derivatives of 5-aminopyrazole underwent the reaction affording 1H-pyrazolo [4,3c][1,5,2]diazaphosphinan-3-one ring system 14, which is the hydrogenated analogue of 2,5-dihydro-1H-pyrazolo [4,3-c][1,5,2]diazaphosphinine and 1H-pyrazolo [4,3c][1,5,2]diazaphosphinine ring systems obtained earlier by us. 19,20 The feature of this cyclization is the difference in nucleophilicity of the two NH-groups of the ureido moiety. The decreased nucleophilicity of the NH-group at the pyrazole allows the reaction to be carried out with PCl 3 , which we had failed to realize with urea 1.…”