Chiral Scaffolds for Enantiocontrolled Synthesis:  Enantio- and Regiocontrolled [4 + 2] Cycloaddition to 3-Alkenyl-η³-Pyranylmolybdenum Complexes

Regio- and Stereospecific Uncatalyzed Reactions of Electron-Rich Arenes and Olefins at Organomolybdenum Enantiomeric Scaffolds

“…Readily available enantiopure, air- and moisture-stable TpMo­(CO) 2 (5-oxo-η 3 -6 H -pyranyl)­and TpMo­(CO) 2 (5-oxo-η 3 -6 H -pyridinyl) complexes, 1 and 2 , and their derivatives are synthetically useful scaffolds for the enantiocontrolled construction of substituted heterocycles (Scheme ; Tp = hydridotris­(pyrazolyl)­borato). − The preparation of multigram quantities of high-enantiopurity complexes is relatively straightforward. , For carbon–carbon and carbon–heteroatom bond constructions, both TpMo­(CO) 2 -stabilized cation ,,,,,− , and anion − , pathways have been observed and applied in the enantiocontrolled synthesis of natural products. The TpMo­(CO) 2 -stabilized carbocations react regio- and stereospecifically with a variety of sp 3 -, sp 2 -, and sp-hybridized Grignard and lithium reagents. ,,,,− Complementing the stabilized cation pathway, a TpMo­(CO) 2 -mediated nucleophilic functionalization pathway was also described. These latter disclosures demonstrate the direct reaction of charge neutral TpMo­(CO) 2 (5-oxo-η 3 -6 H -pyranyl/pyridinyl) complexes, such as 1 and 2 , and TpMo­(CO) 2 (5-acetoxy-η 3 -5,6-dihydropyranyl/pyridinyl) complexes, such as 3a and 4a , with preformed enolates or alkoxide anions. − ,, …”

“…1−24 The preparation of multigram quantities of high-enantiopurity complexes is relatively straightforward. 6,7 For carbon−carbon and carbon−heteroatom bond constructions, both TpMo(CO) 2stabilized cation 1,2,6,8,11,[14][15][16][17][18][19][20]23 and anion 3−5,10 pathways have been observed and applied in the enantiocontrolled synthesis of natural products. The TpMo(CO) 2 -stabilized carbocations react regio-and stereospecifically with a variety of sp 3 -, sp 2 -, and sphybridized Grignard and lithium reagents.…”

Organometallic Enantiomeric Scaffolding: General Access to 2-Substituted Oxa- and Azabicyclo[3.2.1]octenes via a Brønsted Acid Catalyzed [5 + 2] Cycloaddition Reaction

“…1 Short, scalable, and practicable methods of synthesis of high enantiopurity scaffolds TpMo(CO) 2 (3-oxopyranyl) 1 and TpMo(CO) 2 (3-oxopyridinyl) 2 have been developed, 2 and from these simple scaffolds a diverse array of biologically relevant heterocyclic core structures can be obtained in an enantiocontrolled fashion ( Figure 1). [3][4][5][6][7][8][9][10][11][12][13][14][15] The synthetic elaboration of the 3-oxopyranyl and -pyridinyl complexes 1 and 2 often proceeds via the 5-substituted η 3 -pyranyl and -pyridinyl scaffolds 5 and 6 shown in Figure 2.…”

Practical, Scalable, High-Throughput Approaches to η3-Pyranyl and η3-Pyridinyl Organometallic Enantiomeric Scaffolds Using the Achmatowicz Reaction

“…High enantiopurity TpMo(CO) 2 (η 3 -pyranyl) and TpMo(CO) 2 (η 3 -pyridinyl) complexes have proven to be versatile organometallic enantiomeric scaffolds. − Taking advantage of novel trends in reactivity and selectivity, single enantiomers of these air- and moisture-stable pyranyl and pyridinyl organometallic scaffolds have been used in the enantiocontrolled construction of a diverse set of heterocyclic organic systems exemplified in Figure . Of strategic interest in organic synthesis, the principles of organometallic enantiomeric scaffolding allow the development of parallel reaction profiles applicable to both pyran- and piperidine-derived systems, an option not available with traditional organic enantiomeric scaffolds.…”