Eberhard Fuchs

Ungewöhnlich koordinierte Phosphorverbindungen: XXIV. Methylidinphosphan (HCP), ein neuer Cycloadditionspartner für 1,3-Dipole

Abstract Methylidynephosphane ( 2 ) is generated under flash pyrolytic conditions by cleavage of isobutene from the phosphaalkyne ( 1 ) or by elimination of hydrogen chloride from dichloromethylphosphine ( 3 ). It undergoes [3 + 2]-cycloaddition reactions with stable dipoles eq. diazo compounds ( 2 + 4a,b → 5a,b ), methyl azide ( 2 + 7 → 8 ), benzonitriloxide ( 2 + 10 → 12 , 1:2-adduct) and 3-methyl-2,4-diphenyl-1,3-oxazolium-5-olate ( 2 + 13 → 15 ) to give the corresponding phospholes. Silylated phosphaalkene ( 19 ) can be used as a synthetic substitute for 2 : the 5-trimethylsilyl-1 H -1,2,4-diazaphospholes ( 22 ), which result from the reaction of 19 and the diazo compounds 4 with chlorotrimethylsilane elimination, are desilylated to 5 by potassium fluoride in dimethyl formamide.

Phosphatriafulvenes - phosphaalkenes with inverse electron density

The phosphatriafulvenes 3a,b, accessible from the cyclopropenone 1 and the lithium phosphides 2, possess inverse electron density as indicated by structure B; this can also be deduced from ab initio calculations. In accord with the electronic structure, methyllithium attacks at a carbon atom of the three-membered ring (to 45), carboxylic acid chlorides effect P-acylation (to 6), and dimethyl acetylenedicarboxylate inserts into the P/Si bond (to 8).

Organophosphorus compounds - 601. Reactions of phosphatriafulvenes with nucleophilic partners

Abstract The phosphatriafulvenes 1a,b - phosphaalkenes with inverse electron density - react primarily at the three-membered ring with nucleophilic reagents. From their reactions with organolithium compounds 2a-c and Grignard reagents 5a,b the cyclopropenylphosphines 4a-f are obtained after addition of chlorotrimethylsilane; of these products only 4a, d, and e were isolated and characterized. Methanolysis of products 4a-f yields the primary (7a-d) and secondary phosphines (9a,b) via cleavage of the PSi bond. Compound 1b reacts with the ynamines 10a,b through cleavage of the three-membered ring to yield the 1-phospha-1,3,5-hexadienynes 11a (X-ray structure) and 11b. The same phosphatriafulvene reacts with the cyclobutadienes 17a,b to furnish initially the 2-phosphabicyclohexenes 18a,b which, on stirring in chloroform at room temperature, undergo [2 + 2] cycloreversion to give the open-chain isomers 20a,b.