Synthesis of 5-alkylidene-4,5-dihydro-3H-1,2,4(λ3)-diazaphospholes from α-silyl-α-diazoketones and phosphaalkenes

Cycloadducts from Diazocumulenes and 1,2,3(λ3)-Diazaphospholes: Thermolysis Generates Products Derived from 3-Alkenylidene-1,2,3(λ5)-diazaphospholes

“…By analogy to the monocyclic cycloadducts 3, [3] the (E) con-one for the reaction of diazaphospholes 4 with diazoalkanes, [8,11,12] except for the fact that the R 2 C(N 2 ) moiety in figuration of the exocyclic CϭC bond is concluded from the observation of a 5 J P,H coupling (0.9Ϫ1.4 Hz) and of a ArbuzovЈs cases is replaced by R 2 CϭC(N 2 ) in ours. In contrast to some 3-alkylidene-1,2,3(λ 5 )-diazaphospholes, howrather large 4 J P,C coupling (8.6Ϫ9.8 Hz) between the phosphorus nucleus and the nuclei of the ϭC-alkyl (tBu, 1-Ad) ever, the cumulenic analogues 8 do not seem to form bicyclic phosphiranes by a 4π-cyclization reaction.…”

“…These products result from pholes containing a σ 2 λ 3 -phosphorus atom are considered an intramolecular reaction of alkylidenecarbenes derived to have aromatic character according to various theoretical from diazoalkenes 2. [10] Cycloadducts 5aϪl have some characteristic spectro- [a] Abteilung Organische Chemie I, Universität Ulm, scopic features in common, such as a 31 P-NMR signal at Albert-Einstein-Allee 11, D-89081 Ulm, Germany δ ϭ Ϫ4.9Ϫ11.5, a deshielded bridgehead proton (if R 4 ϭ cell is analogous to that of 3a; [3] a detailed comparison of bond lengths and angles is inappropriate, however, due to the limited accuracy of the data in the present case.…”

“…[14] The crystal-structure formed (12). The subsequent 5Ǟ7 ring expansion (12 Ǟ 13) is reminescent of the insertion of DMAD into the Pϭ determination ( Figure 4) 3 was used as solvent. The following references were applied: internal TMS for the proton spectra, the solvent signal for the 13 C-NMR spectra [δ(CDCl 3 ) ϭ 77.0], and external 85% H 3 PO 4 for the 31 P spectra.…”

“…NMR examination ( 1 H, 31 P) of the crude reaction mixture Additional structural proof is provided by the single-crystal X-ray diffraction analysis of 5c (Figure 1). The molecu-indicated again the presence of the expected heterotricyclic compounds 9, but only as a minor component in an even lar structure of the two independent molecules in the unit J P,C ϭ 9.8 Hz, Ad-C-2,-8,-9), 42.6 (d, 3 J P,C ϭ 2.5 Hz, Ad-C-1), 127. 4 Tricyclic 5k behaved like the bicyclic analogues in Scheme 3 and afforded the pentacyclic compound 9k on heating (Scheme 4).…”

Photochemical Isomerizations of 5-Alkylidene-4,5-dihydro-3H-1,2,4(λ3)-diazaphospholes (4-Phosphapyrazolines): (5→4) Ring Contraction Generates Azomethineimine Dipoles

“…Nevertheless, extrusion of molecular nitrogen from 1 (R 1 tBu, 1-adamantyl, Me, 4-anisyl, 4-nitrophenyl) can be achieved in boiling toluene. [7,8] Depending on the substituents, vinylphosphanes, benzo[c]phosphole derivatives, alkylidenephosphiranes, or 1,3-oxaphospholes are formed, and we have proposed that the products are derived from intermediate 1,3-diradicals IV and methylene(vinylidene)phosphoranes V.…”