Carbonylative Stille

Numerous stannanes have been coupled with halopyridines as electrophiles in the Stille coupling. One of the simplest of these is vinylstannane [82-84]. The Stille reaction of bromopyridine 95 with tributylvinyltin gave angustine (96) [84], an indolopyridine alkaloid. Bromopyridine 95 also took part in a three-component carbonylative-Stille coupling sequence to provide an entry to another indolopyridine alkaloid, naucletine (97) [84]. 

Scheme 6 Carbonylative Stille cross-coupling of vinyl halides, triflates, and sulfonyl chlorides.

Several other research groups have also made use of 1-iodo glycals in their syntheses of C-l alkyl and aryl glycals (Scheme 8). Vogel and co-workers reported the use of 1-iodo glycals in carbonylative Stille couplings with... 

An alternative route for installing a methyl ketone is the three component carbonylative-Stille coupling with tetramethyltin. An indolopyridine alkaloid, naucletine (58), was prepared using such a sequence from pyridyl bromide 57 <95CC1675>. 

Another approach developed by the Vogel group relies on a carbonylative Stille cross-coupling between stannylated glucal derivative 410 and enol triflate 412 derived from isolevoglucosenone [152] (O Scheme 80). 

The first enantioselective total synhesis of (-)-strychnine was achieved by L.E. Overman and co-workers. The carbon skeleton of the main precursor for the key aza-Cope rearrangementMannich cyclization was assembled by applying a Pd ° -catalyzed carbonylative Stille coupling reaction. Thus, the cyclic vinylstannane was coupled with the triazinone-protected ortho-iodoaniline to afford 80% yield of the aromatic enone using Pd2(dba)3 as the catalyst in the presence of carbon monoxide. 

A concise synthesis of photoactivatable 4-benzoyl-L-phenylalanines and related peptides was described by G. Ortar et al. using a carbonylative Stille cross-coupling as the key step. Surprisingly, when the coupling was attempted with tyrosine triflate derivatives, it proved to be unsuccessful. However, 4-iodo-phenylalanine derivatives reacted smoothly under standard conditions to give the corresponding 4-benzoyl derivatives. 

Jeanneret, V., Meerpoel, L., Vogel, P. C-Glycosides and C-disaccharide precursors through carbonylative Stille coupling reactions. Tetrahedron Lett. 1997, 38, 543-546. 

The carbonylative Stille coupling is another extremely useful reaction. When the Stille coupling of Ar-X and R-SnR 3 is carried out under an atmosphere of CO, the product is the ketone (ArCOR). An insertion of CO intervenes between oxidative addition and reductive elimination. 

Problem 6.23. Draw a mechanism for the following carbonylative Stille coupling. 

Interactive mechanism for the carbonylative Stille coupling catalytic cycle... 

Scheme 4.26 Pd-catalyzed carbonylative Stille coupling of aryl triflates...

Scheme 4.28 Pd-catalyzed carbonylative Stille reaction with fluorinated alkyl halides...

Scheme 4.32 Pd-catalyzed carbonylative Stille coupling to acetophenones...

In 2010 Nilsson and his group described the carbonylative Stille coupling of aryl triflates and aryl bromides with organostannanes by using Mo(CO)6 as a CO source [72]. Various ketones were synthesized in good yields in closed vessels at 100 °C (Scheme 4.35). In this case, DBU was needed to accelerate the release of CO from Mo(CO)e. 

In 2004, trans- and cw-resorcylide were totally synthesized, and palladium-catalyzed carbonylative Stille coupling was applied for the preparation of the intermediate (Scheme 10.27) [112]. Trans- and cii-resorcylides are both natural macrocyclic plant growth inhibitors, isolated independently from different Peni-cillium species. Together with zearalenone, lasiodiplodin, and the important antitumor agent radicicol, they constimte an important class of bioactive resorcylic macrolides. 

D-homosteroid isolated from a marine source. In 2008 Chen s group reported the total synthesis of this compound by using a palladium-catalyzed carbonylative Stille-coupling of vinyl triflate as the key step (Scheme 10.37) [123, 124]. 

IC50 = 0.09 and 0.037 ng/mL, respectively), as well as in vivo activity against Ehrlich ascites carcinoma. Smith and colleagues reported the total synthesis in 2009 which involve palladium-catalyzed carbonylative Stille coupling as one of the steps (Scheme 10.39) [127]. 

The reactions conducted with organotin reagents were among the first examples of carbonylative couplings to form ketones and were reported by Tanaka and by Beletskaya (Equations 19.77 and 19.78). The relationship between this chemistry and what has been called "Stille coupling" has led these carbonylations to be called "carbonylative Stille... 

Carbonylative Stille coupling of iodobenzene and 1-ethoxy-(1-trimethylstannyUethene... 

A monohapto doubly bridging carbonyl still functions as a 2 electrons ligand the lone pair orbital on carbon can overlap with a suitable in phase combination of filled metal orbitals, while an out of phase combination of filled metal orbitals can interact with the CO n orbital (Figure 23). The net result is to reduce the CO bond order to about 2. 

The carbonylative Stille coupling obeys to the same catalytic loop except that there is a carbon monoxide insertion into intermediate 10 to produce 12, which undergoes the transmetalation step (carbonyl insertion into 12 is faster than transmetalation). 

The Stille-Hegedus synthesis of the diterpene jatrophone took advantage of an intramolecular carbonylative Stille coupling between a vinyl triflate and a vinylstannane motif to forge the macrocycle found in the natural product (see below). 

One pot cascade sequences involving a Stille coupling (Heck/Stille, Heck/ carbonylative Stille, Stille/Diels Alder, Stille/electrocyclization, etc.) have been reported in literature. ... 

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