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The machine program for the determination of fundamental rings is written in the problem-oriented F O R T R A N language. It has already been tested on the IBM@ 7010,7090, and 360 Model 40 machines (the last with a 64 K core memory). A series of different structural-formula graphs with up to 1 2 condensation points were fed into the machine in the short topological form described by Morganr*l, and the fundamental rings present in each were determined by computer.The results were expressed in the form of a list: a heading line that can accommodate up t o 24 two-digit numbers gives the various ring sizes. Under these, in a fourteen line matrix, the individual ring members are given in the order of their occurrence in the ring (cf. Scheme 6).["I Cf. Section 3, 1121.It may happen that in a highly complicated molecule so many condensation points and fundamental rings exist that the available space in the memory of the computer does not suffice for all steps of the complete ring-recognition process. Then the machine prints a message showing which of the condensation points it was unable to consider. After that the result can easily be completed by intellect~ially completing the algorithm. These limitations can be overcome, if necessary, by using a computer with a larger memory or by writing the program in a machine-oriented language instead of FORTRAN.The authors would like to thank W. Schwier and M . Wildgrube fiv substantial niuthen!atical contributionA.When an arenesulfonyl azide, particularly p-toluenesulfonyl azide, reacts, in the prewnce of a base, with a compound containing an active methylene group, the two hydrogen atoms of the active methylene group are replaced by a diazo group to form a diazo compound and an arenesulfonamide. The method may be used for the synthesis of t h e diazo derivatives

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Methods (73)Organophosphorus compounds have been applied in two ways in chemical synthesis. They can either be used as a reagent in a step of the synthesis (for example, in the Wittig reaction) or they can be incorporated directly into the target molecule. This second application, in particular, has expanded greatly in the last few years with the preparation of low-coordination phosphorus compounds. These include the phosphaalkynes, which are of great interest to organic and inorganic chemists. Phosphaalkynes have been employed in the synthesis of heterocyclic compounds, phosphaarenes and their valence isomers, and polycyclic compounds. Further applications have been the use of phosphaalkynes as new ligand systems in complex chemistry and their cyclooligomerization with organometallic reagents. While the chemical properties of phosphaalkynes have little in common with those of nitriles, they are in many ways very similar to those of the isoelectronic acetylenes.

Dedicated to Professor Dieter Seebach on the occasion of his 60th birthday Cyclooligomerization reactions of phosphaalkynes in the coordination sphere of transition metals in which the metal complex fragment is incorporated in the product have played an important role in the development of phosphaalkyne chemistry.[1] Significant examples are the cyclodimerization of tert-butylphosphaacetylene (5a) to give the tricyclic zirconium complex 1, [2] cyclotrimerizations to give the vanadium and hafnium complexes 2[3] and 3, [4] and the formation of the zirconium and hafnium complexes 4[5] by cyclotetramerization. Treatment of 1, 3, and 4 with hexachloroethane leads to detachment of the metal complex fragments and formation of tBu-substituted 1,3,5,7-tetraphosphacubane (cyclodimerization of the residual molecule), [6] 1,3,5-triphosphabenzene (14a), [4] and 1,3,5,7-tetraphosphabarrelene. [5] Reactions of 2 with the same reagent have not yet been investigated. We now report on the chemoselective cyclooligomerization [7] of phosphaalkynes 5 a ± e with the vanadium(v) compounds tBuNVCl 3´D ME (6) [8] (DME 1,2-dimethoxyethane) and tBuNVCl 3 (13) [9] to produce the title compounds in good yields.Reaction of 5 a ± e with 6 in a molar ratio of 4:1 in toluene followed by column chromatography on alumina affords the previously unknown azatetraphosphaquadricyclanes 7 a ± e as yellow solids in yields of 47 ± 76 % (not optimized; Table 1).The elemental analyses and mass spectra (Table 2) indicate that the heteropolycyclic compounds are formed from four molecules of the phosphaalkyne 5 with loss of one molecule of an alkyne RCCR (see Scheme 1) and incorporation of the imide ligand from the vanadium compound 6.As an example the NMR data of 7 a are discussed here (for further spectroscopic data of the compounds 7, see Table 2).[ Table 2. Selected spectroscopic data for the azatetraphosphaquadricyclanes 7.[a]

If one considers the benzene spacers as corners and the ethano bridges as edges of polyhedra. C,,H,, is a tetrahedron. CjnHtr a prism, and C,,H,, a cube. The faces of the polyhedra correspond to the openings on the surface of the molecule. an area suri-ounded by n corners corresponding to a [2.] metacyclophane window (71.

(CH)3P3 structures have been investigated by ab initio (MP4SDTQ/6‐31+G**//MP2(fu)/6‐31G*) and DFT (B3LYP/6‐311+G**) methods. The framework is the main factor determining the realtive energy of isomers; the substitution pattern is less important. The thermodynamic stability order of heteroatom‐substituted benzenes > benzvalenes > Dewar benzenes > prismanes > bicyclopropenyls parallels the situation in the (CH)6 hydrocarbons. The 3 HCP → 1,2,3‐triphosphabenzene trimerization energy is only –84 kcal mol–1; half as large as that for the 3 acetylene → benzene conversion (–164 kcal mol–1). Head‐to‐tail additions are favored for the [4+2] cycloadditions of HCP to 1,2‐ and 1,3‐diphosphete (to give triphospha Dewar benzenes); the computed activation barriers are low: ΔH*298 = 2.2 and 0.8 kcal mol–1, respectively, at MP4/6‐31+G**//MP2(fu)/6‐31G* (2.0 and 1.5 kcal mol–1 at MC‐QDPT2/6‐31G*//CAS‐SCF(6,6)/6‐31G*). Mono‐ as well as ortho‐, meta‐, and para‐diphosphabenzenes and the triphosphabenzenes are found to be as aromatic as benzene according to geometric and energetic criteria. NICS calculations (a magnetic criterion) suggest only slightly reduced aromaticity.