Phosphorus with methylene groups, active

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). 

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 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). 

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

Although strictly outside the remit of this chapter, it is appropriate to note continued activity in the chemistry of c X -p -bonded phosphorus compounds that do not possess a lone pair of electrons at phosphorus. A monomeric metaphosphonate species (262, X=0) has been stabilised by coordination via the P=0 bond), and Harger s group has provided evidence of the intermediacy of metathiophosphonates (262, X=S) in the reactions of phosphonami-dothioic acids with alcohols.The cation (263) has been stabilised by coordination at phosphorus with 4-dimethylaminopyridine and the reactivity of bis(methylene)phosphoranes (264) and related phosphoranylidene car-benoids has been investigated. ... 

Unquestionably, the most attractive procedure for the preparation of dialkyl l-(trimethylsilyl)meth-ylphosphonates is the carbanionic route. The obvious transmetallation difficulties occurring when carbanionic reagents are employed in conjunction with activated methylene groups have led to the development of procedures based on the trapping of a-metallated phosphonates with chlorosilanes in the presence of lithium diisopropylamide (LDA) in excess. For example, the addition at -70°C of chlorotrimethylsilane (1 eq) to a solution of dialkyl 1-lithioalkylphosphonates prepared from dialkyl alkylphosphonates (1 eq) and LDA (2 eq) produces, after workup, dialkyl l-(trimethylsilyl)alkylphos-phonates in 75-90% yields of isolated product, via the quantitative and clean generation of stable dialkyl l-lithio-l-(trimethylsilyl)alkylphosphonates (Scheme Varying the phosphorus reac-... 

Yuan, C., and Li, C., SIndies on organophosphorus compounds. Part 67. Reactions of a-nitroalkenes with compounds bearing active methylene groups. A novel and convenient synthesis of 2-isoxazoline derivatives, Phosphorus, Sulfur Silicon Relat. Elem., 78, 47, 1993. 

The reactive 3-carbonyl group in compounds of type (279) undergoes aldol condensation with active methylene compounds such reactions of isatin with indoxyl, oxindole (Section 3.3.2.5.4) and with thiophenes (Section 3.3.1.5.7.ii) have already been mentioned. These compounds also react with Grignard reagents and phosphorus halides as expected, e.g. isatin (279 Z = NH) with MeMgBr and PC13 yields (285) and (286), respectively. 

The second general method into the thiochrom-4-one ring involves the interaction of a thiophenol with compounds possessing a carbon atom bonded by at least two electron withdrawing groups, usually in the presence of a dehydrating agent (phosphorus pentoxide or poly-phosphoric acid). The first application of this was by Simonis and Elias and is illustrated in Eq. (19). The most successful active methylene substrates have been /3-ketoesters, i )3-cyanoketones, ... 

The first successful syntheses of phosphorus-containing diazoalkyl compounds (1) appear to have been reported independently by two groups of workers. Petzold and Henning employed a method presently described as that of diazo transfer, in which an active methylene compound, as its anion, is treated with an aromatic sulphonyl azide. Seyferth et al on the other hand, reported on a development to the Bamford-Stevens reaction, in which a carbonyl/7-toluenesulphonylhydrazone is treated with a base. Both methods thus depend on modifications to compounds with existing phosphorus-carbon bonds, as do other procedures which have since been developed. 

L abbe and his collaborators have also demonstrated the importance of electronic effects in the synthesis of 1-vinyl-1,2,3-triazoles by adding azides ta either acetylenes (Eq. 15) or active methylene compounds (Eq. 16). In both cases iodoalkyl azides may be added, with comparable results, to produce precursors of 2.2-4 and 2.2-5. This very productive group has pioneered the excellent general method for l,5-disub tituted-l,2,3-triazoles involving phosphorus ylides (Eq. 17). The high yields and wide range of substituents employed makes this method most attractive. Product structures were demonstrated by the Dimroth addition and decarboxylation (Eq. 16). 

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