Parham cycloalkylation

Paraxanthine—see Xanthine, 1,7-dimethyl-Parent name nomenclature, 1, 35 Parham cycloalkylation in chroman synthesis, 3, 783 Paromomycins as pharmaceuticals, 1, 154 Partial charge transfer from donor to acceptor stacks, 1, 350 Pasteurellosis... 

Several chromans have been synthesized using the Parham cycloalkylation technique (76JOC1184). l-Bromo-3-(2-bromophenoxy)propane, prepared from phenol and 1,3-dibromopropane, is treated with n-butyllithium at — 100 °C. Halogen-lithium exchange yields the aryllithium (278) which cyclizes either at — 100°C or in some instances only at an acceptable rate at higher temperatures. This method offers the advantage of regio-specificity since cyclization is controlled by the location of the o-bromine atom (Scheme 72). 

The Parham cycloalkylation has been extended to provide a general route to oxygen heterocycles thus the reaction of (141) with butyl-lithium at — 100°C, followed by warming to 25°C, gives the 1-benzoxepin (142) in > 70% yield. ... 

Parham cycloalkylation 343 Patemo-Btichi reaction 46 von Pechmann synthesis (coumarin) 322 Pellizari synthesis (1,2,4-triazole) 270 Perkin rearrangement 82 Pfitzinger synthesis (quinoline) 398 Pictet-Gams synthesis (isoquinoline) 414 Pictet-Spengler synthesis (isoquinoline) 415 Piloty-Robinson synthesis (pyrrole) 119 Pinner synthesis (pyrimidine) 467 Plancher rearrangement 128 Polonovski reaction 545 Pomeranz-Fritsch synthesis (isoquinoline) 415 Prileschajew reaction 23 Prins reaction 452 Pummerer rearrangement 26, 457... 

---