A convenient access to nitriles having a variety of extremely different structures is provided by the ylide anion 1, which is isolable as the sodium salt. By reaction with alkyl halides RX, 1 can be converted into cyclic α,β‐unsatu‐rated nitriles such as 2; the “dienyl cyanides” 3 and alkynyl cyanides RCCCN are obtainable from 1 by reaction with aldehydes RCHO and esters RCOOR', respectively.

A. The mechanism of the Wittig reaction is re-interpreted on the basis of new experimental and theoretical results. B. Reactions of trimethylsilylated phosphorus ylides are described. They allow a reversal of the stereochemistry of the Wittig reaction. C. The preparative possibilities of the reaction of N-phenyl-ketenylidenetriphenylphosphorane with carbon acids are presented and the synthesis of the tetramer of phenyl isonitrile is reported. D. The results of investigations into the reactions of Hexaphenylcarbodiphosphorane are presented. A. The Wittig Reaction Detailed investigations have led us to propose a new mechanism for the Wittig reaction.123 Ylides, (1), and aldehydes, (2), combine to give oxaphosphetanes, (3), in which the 0-atom occupies an apical position on the pentavalent phosphorus and in which the substituents on the four membered ring are B to one another. Cleavage of the original. ylid C-P bond, which is necessary for formation of the olefin, requires a ligand reorganisation process (pseudorotation) which brings this bond to an apical position,The opening of the C-P bond to give the betain (5) occurs during or after the conversion to the trigonal bipyramidal structure (u).The electronic nature of the substituents R1 and R2 in (5) is instrumental in determining the stereochemistry of the product olef in. When R1 phenyl electron donating R2 substituents cause a very fast elimination of the phosphine oxide, giving B olefins (7). Electron-withdrawing R2 groups (R1phenyl) extend the lifetime of (5), which can now isomerise to the thermodynamically more stable (6), from which phosphine oxide elimination gives E-olef ins (8). If the ligands R1 on phosphorus are electron-donating the rate of the phosphine oxide elimination is also decreased. In this case strongly increased formation of E-olefins is observed, compared to R1C6H5, even when R2 is an electron donor.

Alkynes Alkynes P 0027Further Improvements of the Synthesis of Alkynes from Aldehydes. -The method presented allows the generation of the required dimethyldiazomethylphosphonate in situ. It avoids the use of strong bases, low temperature and inert gases. -(ROTH*, G. J.; LIEPOLD, B.; MUELLER, S. G.; BESTMANN, H.

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I85 ( 8 5 ) The Wittig reaction of ( 4 ) with aldehydes affords N-substituted thiocarboxamides (7) of cc,(j-unsaturated acids. Both ( 3 ) and ( 4 ) undergo S-methylation on treatment with methyl iodide; the phosphonium salts ( 5 ) isolated after this reaction can be converted into the ylides ( 6 ) by treatment with sodium methoxide. Starting from ( 6 ) , hydrolysis gives thioimidic acid derivatives (a), Wittig reaction affords the corresponding derivatives of cc,P-unsaturated acids ( 9 ) , and reaction with methyl iodide leads to the substituted vinylphosphonium salts ( 10). Angew. Chem. 77, 609, 651, 850 (1965); Angew. Chem. internat. Edit. 4, 583, 645, 830 (1965 Cycloalkanes having an exocyclic double bond and an even number of C atoms in the ring, which bears a substituent at the greatest possible distance from the double bond, are chiral molecules [type (I)]. The same applies to all cis-disubstituted cycloalkanes with a exocyclic double bond having two identical substituents at equal distances from the double bond [type (2)]. In both cases it is essential that R and Rl + H, although R = RI is possible. We have found that optically active molecules of types (f) and (2) can be obtained by partial asymmetric synthesis, the route selected being a Wittig reaction of the corresponding ketones with optically active alkylidenephosphoranes. We chose benzylidenemethylphenyl-n-propylphosphorane (3) (71, m.p 1 175(70) as the optically active ylide since the absolute configuration of the phosphonium bromide obtained from ( 2 ) on liberation of HBr by sodamide is knownr21.