... VoL 35. No. ... 4-ones (lo,p). Sample of 9.9 mmol of thiourea and two drops of 88% formic acid were added to solution of 8.25 mmol of compounds Ib,f ... Vlla-c). Sample of 8.8 mmol of thiourea and two drops of 88% formic acid were added to solution of 7.36 mmol of compound Via-c ...