Vier‐ und fünfgliedrige Phosphorheterocyclen, 36 ¹⁾ 1,3‐Dipolare Cycloadditionen an Azaphosphole und Azaphospholine

Abstract

and azaphospholines (4), give stable [3 + 21-cycloadducts (3, 5, 8, 9, 11) with arylnitrile oxides, diphenylnitrile imine, and nitrones which can be isolated in crystalline form. The bridgehead position in the bicyclooctane structure of the adducts favours phosphorus pentacoordination and thus enhances adduct stability; NMR spectroscopic results agree to the meridional arrangement of the bicyclus. The cycloaddition to azaphospholes depends on the 1,3-dipoles in an order known from other dipolarophiles and decreases with the phosphorus substituents Me > Ph > NMe,. The adducts of the 3,4-dihydroisoquinoline N-oxide (11 f, g) dissociate reversibly in solution.1,3-Dipolare Cycloadditionen a n Phosphanmethylene und Phosphanimide wurden wiederholt untersucht. Jedoch liefern nur die ersteren in gunstigen Fallen mit Nitriloxiden '3 3, und Nitronen 4, tatsachlich Cycloaddukte mit pentakoordiniertem Phosphor. Phosphanimide reagieren damit entweder iiberhaupt nicht oder ergeben, offenbar iiber die Cycloadditionsstufe hinweg, Phosphanoxide als deren Zerfallsprodukt 5 , (1).Nitrilimine addieren sich entweder gar nicht oder, wenn die auftretenden Ladungen stabilisiert werden konnen, lediglich zum Betain ').Phosphanimide, in denen die Phosphazengruppe Teil eines Funfrings ist, zeigen gegeniiber dem acyclischen Normalfall bei [2 + 21-Cycloadditionen eine gesteigerte Reaktivitat und hohere Adduktstabilitat 'I. Sie ist auf die Begiinstigung der Phosphorpentakoordi-

Molecules that we made: An essay on phosphorus chemistry

“…With ketones, we observed the occurrence of an aza-Wittig reaction, of which the intermediate 22 can be isolated [65,66]. We also obtained adducts with CO 2 and CS 2 [67], isocyanates [68], isothiocyanates [69], ketenes [70], iminophosphines and iminophosphoranes [71], epoxides [72], nitrones, nitrile oxides, and nitrile imines [73,74]. A one-pot combination of the two mentioned types of cycloaddition was found in the reaction of the methyleneaminophosphite (MeO) 2 P-N‫ס‬CPh 2 with p-nitrobenzaldehyde [75]; four acyclic molecules combine to form the tricyclic structure 23.…”

Introducing N-Heterocyclic Iminophosphoranes (NHIPs): Synthesis by [3 + 2] Cycloaddition of Azophosphines with Alkynes and Reactivity Studies

“…The rigid cyclic structure enabled selective anion recognition via hydrogen bonding, which was essential for achieving high enantioselectivity. − A rigid cyclic structure is also advantageous for the stabilization of reactive main-group or metal species by preventing decomposition by steric shielding. In this context, cyclic iminophosphoranes ( 1 and 2 in Scheme C), having geminal aromatic substitutions α to the basic nitrogen, were prepared by 1,3-dipolar cycloaddition of phosphinoimine (Ph 2 CN–PR 2 ) and dimethylacetylene dicarboxylate (DMAD). − The resulting cyclic iminophosphorane 1 was used as a ligand for gold­(I), but further reactivity studies have not been pursued presumably because of the extreme steric crowding at the basic nitrogen atom. Recently, the cycloaddition of MesNNP A ( A = anthracene) and cyclooctyne was disclosed, where a nucleophilic phosphorus center and an electrophilic NN π* component enabled MesNNP A to react as a 1,3-dipole (Scheme A) .…”