Conformationally restricted pyrrolidines by intramolecular [2+2] photocycloaddition reactions

Abstract

Intramolecular [2+2] photocycloaddition reactions of diversely substituted N-Boc protected 4-(allylaminomethyl)-2(5H)-furanones resulted in rigid products (53-75%) with three spatially defined positions for further functionalisation.

An Intramolecular [2 + 2] Photocycloaddition Approach to Conformationally Restricted Bis-Pyrrolidines

“…Other 3-aza-9-oxatricyclo[5.3.0.0 1,5 ]decan-8-ones with substituents at the 7-position (X 3 = Ph, Me, F; 9 in Table ) and at the 5-position (X 1 = Ph, Me; 10 in Table ) have been previously described . In the present study, it was shown that their conversion to the conformationally restricted bis-pyrrolidines 11 and 12 could be performed in full analogy to the previously described conversion 3 → 6 .…”

“…Although there have been a few scattered reports on the synthesis of molecules with the 3,9-diazatricyclo[5.3.0.0 1,5 ]decane skeleton A , a general approach has, to the best of our knowledge, not yet been reported. Since previous studies have shown that lactones of type B can be generated by intramolecular [2 + 2] photocycloaddition reactions of appropriately substituted 4-aminomethyl-2(5 H )-furanones, , we considered them as potential precursors of the desired products A . In this report, we describe the synthesis of both latently symmetric (X 1 = X 3 ) and nonsymmetric (X 1 ≠ X 3 ) 3,9-diazatricyclo[5.3.0.0 1,5 ]decanes employing an intramolecular [2 + 2] photocycloaddition as the key step.…”

Recent Advances in the Synthesis of Cyclobutanes by Olefin [2 + 2] Photocycloaddition Reactions

“…In an approach to conformationally rigid pyrrolidines and bis-pyrrolidines the intramolecular [2 + 2] photocycloaddition of various 4-(allylaminomethyl)-2(5 H )-furanones was investigated. 567 − 569 The reactions (e.g. 309 → rac - 310 ) were found to proceed best under conditions of direct irradiation ( Scheme 100 ).…”

Selective preparation of tetrasubstituted fluoroalkenes by fluorine-directed oxetane ring-opening reactions

“…The latter was subjected to the HBr/AcOH ring-opening reaction conditions ( Scheme 6 ). Remarkably, the cyclic products β-hydroxymethyl and β-bromomethyl-γ-lactones 17 and 18 were obtained in an 8:92 ratio [ 32 ]. This complete reversal of selectivity in comparison with fluoroalkylidene-oxetane 12 , where the β-hydroxymethyl-γ-lactone 14 was obtained, confirmed an electronic influence of the fluorine atom on these ring-opening reactions ( Table 3 , entries 1 and 2).…”