By Miscellaneous Routes

Several minor routes to. V-alkylpipcrazincs are illustrated in the following examples  

4-Methylpiperazin-l-ylmagnesium bromide (made in situ) and crude 3-chloro-4-methylthio-l,l-diphenylsilolane (228) [made in situ from the 2,5-dihydrosilole (227), Me2S2, and S02C12] gave l-mcthyl-4-(4-mcthylthio-l,l-diphenyl-silolan-3-yl)piperazine (229) (THF, 20°C, 12 h 50%, as oxalate salt).1182 

6-Tetraphenylpyrazine gave an (unformulated) disodium dianionic adduct (233) (excess Na, THF, 20°C, A, 24 h solution filtered) that reacted with Mel to give a separable mixture of l,2-dimethyl-2,3,5,6-tetraphenyl-l,2-dihy-dropyrazine (234, R = Me), l,2,4,5-tetramethyl-2,3,5,6-tetraphenylpiper-azine (235), and 2-methyl-2,3,5,6-tetraphenyl-l,2-dihydropyrazine (234, R = H) [Mel (2 mol), -78 20°C, 4 h 45,18, and 23% respectively].492 

4-pyridazinamine (236) gave 2-(4-methylpiper rzin-l-yl)-4-phcnylpyrido[2,3-r/lpyridazine (238) (neat reactants, 130°C, 15 h 56%)35  

At the P=0 or P=S Group.—An extremely simple and efficient synthesis of thiirans by treating oxirans with the phosphine sulphides (28) has been reported. The reaction is catalysed by molar quantities of 

Previous suggestions that the peracid oxidation of secondary phosphine oxides involves (33) as an intermediate have been confirmed from studies 

Miller, in Organophosphorus Chemistry , ed. S. Trippett (Specialist Periodical Reports), The Chemical Society, 1972, vol. 3, p. 63. 

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Synthesis of the Second Heterocyclic Ring by Miscellaneous Routes 904... 

By Miscellaneous Routes.—The synthesis of cyclic phosphine oxides from a,co-dibromides and tetraphenyldiphosphine has been described (Scheme 5). The intermediate phosphonium salts are converted into the... 

Most of these phthalazinones have been made by primary synthesis (see Chapter 8). A few have been made also by direct C-hydroxylation (see Sechons 9.1.3 and 9.2.2), by hydrolysis of halogenophthalazines (see Section 10.3.3), or by miscellaneous routes illustrated in the following classified examples. 

Miscellaneous Routes. Polyamides have been prepared by other reactions, including addition of amines to activated double bonds, polymerization of isocyanates, reaction of formaldehyde with dinitriles, reaction of dicarboxylic acids with dllsocyanates, reaction of carbon suboxide with diamines, and reaction of diazlactones with diamines. These reactions are reviewed in Reference 4. 

Thioxo-1,2,4-dithiazolidines can be obtained from thioxo-l,2,4-thiadiazolidines by Dimroth rearrangement (Scheme 47) or reversibly by addition and elimination of acetone (Scheme 22). 1,2,4-Dithiazole type products are also obtained from thiocarbonyl isothiocyanates (154) by reaction with CI2 <84CHEC-I(6)897>, PhMgBr, Sj, or CS2. Other routes include reactions of carbonyl isothiocyanates and thiocarbonyl isocyanates with P4S10 or Sg <84Chec-I(6)897> and sulfonyl isocyanates with dialkyl thioketenes. Phenylisothiocyanate heated with N,C-disubstituted oxaziridines affords 3,5-diimino-l,2,4-dithiazolidines (226, 227). Other miscellaneous syntheses of 1,2,4-dithiazoline derivatives include cyclization of A7-thioacyl hexafluoroacetonimine to 5,5-bis(trifluoromethyl)-... 

Miscellaneous Reactions.- Thermolysis of 5-hydroxyphosphonium ylides (67) provides a useful route to a,p-unsaturated ketones. The ylides (67) have been prepared by the reaction of an appropriate ylide (66) with propriolactones, although the success of this method depends on the cation of the base used in the generation of (66). An alternative and more generally useful method of generating (67) from acylated ylides (68) has now been... 

Miscellaneous Methods of Preparing Phosphines. Approaches to the synthesis of specific types of organophosphine have been reviewed, covering phosphinoaryloxazolines, /ra j-2,5-disubstituted phospholanes, " new chiral phosphines which have been reported since 1990, chiral hydroxyphos-phines, and phosphorus-sulfur donor ligands.The uses of phosphine (PH3) in the synthesis of organophosphines has also been reviewed. A direct route for the synthesis of arylphosphines is offered by the reaction of... 

Miscellaneous Reactions. In two comprehensive publications, Taylor and co-workers detail the reactions of 1,2-dioxines with stabilised ylides as a route to diastereomerically pure cyclopropanes (Scheme 18). The reaction of ozonides with stabilised ylides produces a,p-unsaturated carbonyl compounds (Scheme 19). The E/Z isomeric ratio of the final products is affected by the identity and position of heteroatom substituents on the ozonide heterocycle. ... 

The use of natural gas for manufacture of various chemicals via the syngas route or via direct methanation or via other miscellaneous methods is very important for chemical industries. However, the production of all the desired chemicals is accompanied by formation of byproducts and some end products, which when released into the environment constitute pollution hazards. 

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