Stannanes reduction

The stannane reduction is also applicable to selenocarbonates (2) of primary and secondary alcohols (equation II) and can result in the noralkane, the formate, or the... 

Binary hydride (boranes, alanes, silanes, stannanes) reductions of oxygen-containing compounds are used in organic synthesis , e.g., with ketones ... 

Interesting coupling reactions can be earned out with alkenyl- and alkynyl-stannanes. Reductive eoupling of aeid ehlorides with ( )-l,2-bis(tri-n-butylstannyl)-... 

More recently, the use of the AMI method in predicting enantioseleclivities during stannane reductions has also been examined [33]. In preliminary work, Schicsscr and coworkers found that the AMI molecular orbital method is capable of correctly predicting the preferred stereochemistry, as well as the stereo-enhancing effect of Lewis acids, during the delivery of hydrogen atom from a series of chiral non-... 

A less ambiguous example of addition to the oxygen atom, reported by Kuivila, is the stannane reduction, catalyzed by AIBN, of y-chlorobutyrophenone (191), which gave a mixture of AH and Cy5H (ratio 20 80) in 65% yield (Scheme 84). This unexpectedly easy cyclization to the... 

Often the cyclized radical opens in the other direction to give rearranged products. This possibility has been used to explain the results of the pyrolysis of cyclopropyl acetates, of the lead tetraacetate oxidation of a-acetoxy alcohols,and of the stannane reduction of a-acetoxy chlorides. In all these cases free radical addition followed by -scission has been proposed, e.g., as in the 1,2-rearrangement of )ff-acyloxyl radicals 205 to 207 (Scheme 90) discovered independently by Teissier and by Tanner,and whose mechanism, while not completely elucidated, is presumed to proceed through 206, which must be considered as a transition state rather than an intermediate. 

In all the examples so far reported the initial ring in the substrate was a Cy5 or Cy6 ring. Other possibilities are, of course, available, such as a Cy3 ring. Such an example has been reported by Julia (Scheme 110). Tributyl-stannane reduction of 269 gives the radical 270, which cyclized exclusively toward the (Cy 5) radical 271. The main cyclized product was the endo compound 272 (71% yield), and the minor one the exo compound 273 (14% yield). This cyclization process was not observed with compounds bearing methyl substituents on the cyclopropane ring or on the aliphatic chain. . ... 

Another interesting example of free radical polycyclization leading to bridged compounds has been described by Beckwith (Scheme 149). The radical 411 generated by stannane reduction of the corresponding bromide... 

A difTerent approach to polycyclization reactions has been reported with acetylenic compounds such as 421 (Scheme ISO). By stannane reduction one obtains compound 425 in low yield. The reaction involves formation of the radical 422, which cyclizes to the (Cy 5) radical, which then gives 423, and this, on further reduction, gives 424, which cyclizes to the (Cy S ) radical and finally gives 425. 

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