Substituent effects in the asymmetric Diels-Alder cycloaddition of 3,4,5-triaryl-1-(+)-neomenthyl-1,2-diphospholes’ with maleic acid derivatives

Oxophosphonium-alkyne cycloaddition reactions: reversible formation of 1,2-oxaphosphetes and six-membered phosphorus heterocycles

“…Our computational results indicate that the acyclic 1-phospha-4-oxa-butadiene state of [ 2a ] + is thermally accessible, which prompted us to investigate whether it can be trapped by [4 + 2] hetero Diels–Alder cycloaddition reactions. Similar to α,β-unsaturated carbonyls, which are important dienes in hetero Diels–Alder reactions for material and natural product synthesis, phospha-butadiene derivatives have been used in cycloaddition reactions for the construction of phosphorus-containing heterocycles. − Furthermore, neutral σ 3 λ 5 -phosphoranes containing the PC–­CO system were postulated as reactive intermediates based on their ability to undergo [4 + 2] cycloaddition reactions with polar multiple bonds. , …”

Review on asymmetric cycloaddition reactions at phosphorus (III) atom

“…11 At the same time, asymmetric Diels-Alder reactions of 1-(+)-neomenthyl-3,4,5triaryl-1,2-diphosphole (1b) with maleic acid derivatives proceeded with higher diastereoselectivity (up to 91% de) and results in the corresponding enantiopure 1,7-diphosphanorbornenes 3 after recrystallization. [12][13][14] An analysis of the structure of 1-(+)-neomenthyl-3,4,5-triphenyl-1,2-diphosphacyclopenta-2,4-diene (1b) indicated that steric shielding of one side by the bulky isopropyl group causes a preferential approach of the dienophile from the opposite side resulting in one attractive and one repulsive pathway of the [4+2] cycloaddition reaction. This study approves that getting closer of the chiral inductor with the dienic system of 1,2-diphospholes leads to an increase of stereochemical outcome (de) of hetero-Diels-Alder reaction.…”

Thiophosphonium–Alkyne Cycloaddition Reactions: A Heavy Congener of the Carbonyl–Alkyne Metathesis

“…The heavy atom α,β-unsaturated ketones contain reactive double bonds and thus provide a platform for rich follow-up chemistry. Phosphabutadiene derivatives have been extensively used in cycloaddition reactions for the construction of phosphorus-containing heterocycles, − and many examples of P=C–C=O compounds reacting in hetero-Diels–Alder reactions were reported. , Since the analogous reactivity with a P=C–C=S moiety is unexplored, we attempted to identify substituent effects that would stabilize this acyclic structure. The rather low transition state with ethoxyacetylene indicates that electron-donating groups might be beneficial in this respect.…”