Organic Synthesis. Use of Alkynes as a Key to Innovation in Designing Structure for Function

Abstract

A personal perspective of one aspect of what needs to be done to fulfill the scientific objective of improving the world in which we live is presented. One specific goal of this journey is to enable the best design of molecular structure for function regardless of complexity. Meeting this objective requires improvements in the fundamental tools of constructing synthetic reactions. What is presented is just one part of our journey which started with a fundamental question; do the unique features of alkyne building blocks provide an unusual opportunity to achieve the noted objectives? The story begins with the discovery of new synthetic tools and concludes with numerous illustrations of the broad potential these tools appear to possess.

Microwave‐Assisted Synthesis and Transformations of Cationic CpRu(II)(naphthalene) and CpRu(II)(naphthoquinone) Complexes

“…Ellipsoids are represented with 50 % probability. Selected bond distances: Ru(1)À C(1) and Ru(1)À C(1 i ) 2.218(3), Ru(1)À C(2) and Ru(1)À C(2) i 2.214(4), Ru(1)À C(3)and Ru (1)À C(3) i 2.257(3), C(1)À C(1 i ) 1.419(8), C(1)À C(2) 1.410(5), C(2)À C(3) 1.433(5), C(3)À C(3 i ) 1.439 (7), C(3)À C(4) 1.443(5), C(4)À C(5) 1.341(5), C(5)À C(5 i ) 1.429(8).…”

“…Microwave heating shortens the time of synthesis of [Ru(II)Cp(naphthalene)][PF 6 ] (2) from ruthenocene from three days to 15 minutes. This complex serves as an excellent air-stable precursor for the widely used (7), C(3)À C(8) 1.454 (7), C(4)À C(5) 1.359 (8), C(5)À C(6) 1.425 (8), C(6)À C(7) 1.365 (8), C(7)À C(8) 1.436 (7), C(8)À C(9) 1.439 (7), C(9)À C(10) 1.408 (8). catalyst [Ru(II)Cp(CH 3 CN) 3 ][PF 6 ] (1).…”

“…[5] Ru-complex 1 and derived catalysts were used primarily by Trost and coworkers for CÀ C coupling reactions. [6,7] His group as well as others applied these efficient catalysts in natural product syntheses. [8 -14] Lacour and coworkers used 1 in asymmetric Caroll rearrangements and related reactions as well as in catalytic carbene CÀ H insertion and condensation reactions.…”

BCl3-Mediated C–N, C–S, and C–O Bond Formation of Imidazo[1,2-a]pyridine Benzylic Ethers

“…Considering the gradual decrease in molarity of BCl 3 solution over time due to high volatility of BCl 3 , 1.4 equiv of BCl 3 was used, an improvement in yield (32%) of the desired product 2a (entry 2) was noticed. 16…”

Mechanistic Study of Pd/NHC‐Catalyzed Sonogashira Reaction: Discovery of NHC‐Ethynyl Coupling Process

“…Functionalized acetylenes play ak ey role in natural products, are actively utilized as synthetic intermediates,a nd find their applicationsi np harmaceuticals and organic materials. [1][2][3] Over the last decades, Sonogashira coupling has become one of the key approaches towards alkyne functionalization in modern organic synthesis. [4][5][6][7][8][9][10][11][12] Amongst numerousp alladium catalysts utilized in this transformation Pd/NHC (NHC = N-heterocyclic carbene) complexes have firmly established their utility as highly-active catalystsw hich are much more stable towards air and moisture than popular Pd-phosphine complexes.…”