Phosphorus with methylene groups

Polymerization of 4-bromo-6,8-dioxabicyclo[3.2.1 ]octane 2 7 in dichloromethane solution at —78 °C with phosphorus pentafluoride as initiator gave a 60% yield of polymer having an inherent viscosity of 0.10 dl/g1. Although it is not described explicitly, the monomer used seems to be a mixture of the stereoisomers, 7 7a and 17b, in which the bromine atom is oriented trans and cis, respectively, to the five-membered ring of the bicyclic structure. Recently, the present authors found that pure 17b was very reluctant to polymerize under similar conditions. This is understandable in terms of a smaller enthalpy change from 17b to its polymer compared with that for 17a. In the monomeric states, 17b is less strained than 17a on account of the equatorial orientation of the bromine atom in the former, whereas in the polymeric states, the polymer from 17b is energetically less stable than that from 17a, because the former takes a conformation in which the bromine atom occupies the axial positioa Its flipped conformation would be even more unstable, because the stabilization by the anomeric effect is lost, in addition to the axial orientation of the methylene group. 

A comparison of 1,3,5-dioxaphosphorinanes with the corresponding 1-phenylphosphorinanes shows that substitution of the methylene group by oxygen results in a shift of the equilibrium toward the conformer with an axial orientation of substituent at phosphorus. 

An interesting report has been made of methylene insertion into the P-C linkage of a-(acyloxy)iminoalkylphosphonates derived from carbohydrates.181 This reaction system, using diazomethane, allows extension of the chain by a single carbon atom, with that atom (methylene group) attached directly to the phosphorus. 

The phosphonic group can be introduced in position 4 of a pyran ring (66) by utilization of phosphorus-containing UN 67 in a reaction with methylene-active ketones 35 or 36 on continuous heating in ethanol (00PS(165)17) (Scheme 15). 

The cyanobromide (371) was condensed with the bc portion (347) to give the thioether (372) sulfide contraction to give (373) was accomplished using tris(/3-cyanoethyl) phosphine, and with phosphorus pentasulfide the thiolactam-thiolactone (374) was produced. After treatment with Meerwein s salt, reaction with dimethylamine opened the lactone with concomitant formation of an exocyclic methylene group, and subsequent treatment with cobalt chloride or iodide gave the chelate (375) which was reacted with diazabicyclononane to give bisnorcobyrinic add [Pg.435]

Russian workers (74KGS58) carried out Vilsmeier reactions on 4,5-disubstituted 2-acylthienylamines and cyclized the resulting 3-formyl compounds with substances containing active methylene groups (Scheme 60). A versatile new synthesis of thieno[2,3-6]pyridines is also based on the Vilsmeier formylation of 2-acetamidothiophenes. Whereas with equimolar amounts of DMF and phosphorus oxychloride 3-formyl derivatives are obtained,... 

In a few instances group activation is coupled to cleavage of ATP at C-5 presumably with formation of bound tripolyphosphate (PPP ). The latter is hydrolyzed to Pj and PPj and ultimately to three molecules of P. An example is the formation of S-adenosyl-methionine157 shown in Eq. 17-37. The reaction is a displacement on the 5 -methylene group of ATP by the sulfur atom of methionine. While the initial product may be enzyme-bound PPP , it is P and PP that are released from the enzyme, the P arising from the terminal phosphorus (P.,) of ATP.157 The S-adenosyl-methionine formed has the S configuration around the sulfur.158... 

The a- and y-methylene groups of pyrylium salts condense with pyranones and ben-zopyranones when the salts are heated in acetic anhydride or phosphorus oxychloride. Some of the resulting compounds are potentially interesting as dyes, for example the tripyran (110) (68JOC4418). In hot acetic anhydride equimolar amounts of the salt (111) and flavone condense to give a green-coloured salt (112) (78AP236). 

The formation of acylnaphthalenes 225 occurs under mild conditions (catalysis by sodium rm-butoxide or with the use of the phase-transfer method and TEBA as catalyst), and it affords high yields (60-90%). In this connection, it is surprising to recall the opinion about the incapability of 2-benzopyrylium salts to take part in recyclization reactions with compounds possessing active methylene groups, with secondary amines, or with sulfur or phosphorus nucleophiles (71CB2984). 

The 3-phospholene 1-oxide derivative is a potential heterocycle for easily producing chemically modified phosphorus heterocycles because the compound possesses a reactive C=C double bond, allylic methylene, an electron-deficient methylene group a-positioned to phosphorus, etc. 4-Chloro-l,6-dihydrophosphinie derivatives 16A and 16B are prepared from dichloro-carbene adducts 15 with l-(R)-3-ethylphospholene 1-oxide (Scheme 5) [4]. 

Synthesis of Phosphorus-containing Indoles Using Organophosphorus Compounds with Active Methylene Group... 

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