Silver Mediated Cyclizations of 4-Allenyl-and 4-(2-Propynyl)azetidinones. A Stereoselective Synthesis of 3-Substituted Δ1-Carbapenems Via N-C3 Closure.

Total Synthesis of Clavepictines A and B. Diastereoselective Cyclization of δ-Aminoallenes

“…In contrast to the oxygen-containing heterocycles, the intramolecular cyclization of ω-amino allenes has been limited to a handful of monocyclic ring formations; to our knowledge, only a single application was reported for the stereocontrolled synthesis of nitrogen-containing bicyclic rings 21a. Particularly relevant is Gallagher's enantioselective synthesis of ( R )-(−)-coniine ( 35 ) (Scheme ), in which silver(I)-catalyzed cyclization of chiral allene 36 was demonstrated to take place with little racemization (<4−10%) to produce 38 21d. Exceptional chirality transfer was rationalized in terms of the intermediacy of a dissymmetric silver−allene complex 37 .…”

Silver and platinum-catalysed addition of O–H and N–H bonds to allenes

“…28 However, reactions through the nitrogen nucleophile have also been reported. For example pyrroloisoindolones and the corresponding pyrroles can be obtained in moderate yields by reaction of allenyl 1-isoindolinones with 40 mol% of AgNO 3 (Scheme 40a), 46 D 1 -carbapenems have been obtained by reaction of 4-allenylazetidones with AgBF 4 (0.5-2 equivalents) (Scheme 40b), 47 and pyrrolidine azasugar precursors have been synthesised from allenyl carbamates (Scheme 40c). 48 The only example in the literature of reaction of b-amino allenes was reported by Alcaide, Almendros et al using an alleneb-lactam derivative to form the tetrahydrofuro[3,2-b]piperidine core present in several natural products (Scheme 41).…”

Development of Useful Reactions Involving Tandem Cyclizations Based on the Novel Reactivities of Allenic Compounds

“…35,36) Particularly, cyclization of amino allenes using such metals as Pd(0 or II), [37][38][39][40][41][42][43][44][45] Ag(I), [46][47][48][49][50] and organolanthanides 51) has become quite useful methodology for the synthesis of fiveor six-membered azacycles, and several groups have applied such cyclization to the total synthesis of natural products. [52][53][54] It is well documented that cyclization of amino allene 30 with a one-or two-carbon tether between the allene and the nitrogen atom (nϭ1 or 2) yields five-or six-membered azacycles 31 (nϭ1 or 2) selectively by path A (Chart 5), while an amino allene bearing a longer carbon tether (nϭ3 or 4) also affords five-or six-membered rings 32 (nϭ3 a) Reactions were carried out in THF at room temperature under argon using Pd(PPh 3 ) 4 (10 mol%) and Et 2 Zn (2 eq), unless otherwise stated.…”