Contrasting Diastereofacial Selectivity Associated with N-Phenyltriazolinedione Cycloadditions to Oxaspirocycloheptatrienes

Abstract

[reaction: see text] The cycloaddition of N-phenyltriazolinedione to a pair of spirocyclic cycloheptatrienes featuring a tetrahydrofuran or tetrahydropyran ring is shown to proceed with opposite pi-facial stereoselectivity. In addition, the furan undergoes direct [4+2] cycloaddition to the cycloheptatriene whereas the pyran product is a diazetidine.

Development of Domino Processes by Using 7‐Silylcycloheptatrienes and Its Analogues

“…For instance, hetero-Diels-Alder reaction between 4 b and triazolinedione [27] led to the expected norcaradiene cycloadduct 15 as a single endo-isomer (X-ray) (Scheme 5). When treated with CuA C H T U N G T R E N N U N G (OTf) 2 , 15 led, after cleavage of the C À N bond and subsequent cyclopropane ring opening, to the cyclohexa-1,3-diene 16 in modest yield.…”

Concerning the Reactivity of PTAD with Isomeric Dienes: The Mechanism of the Diels−Alder Cycloaddition

“…Triazolinedione (RTAD, R = M for methyl and R = P for phenyl) is a strong electron acceptor and one of the most powerful enophiles as well as dienophiles . RTADs afford ene products ( N -allylurazoles) or [2 + 2] adducts (1,2-diazetidines) , with alkenes and undergo DA reactions with conjugated dienes. , The latter class of reactions is useful in characterizing dienes, protecting diene moieties, isolating dienes from complex reaction mixtures, and trapping unstable or volatile intermediates …”