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5.2.1.4.1.1 Variation 1: Reduction of Carbon—Halogen Bonds

DOI: 10.1055/sos-SD-105-00166

Tchabanenko, K.Science of Synthesis Knowledge Updates, (2013112.

Reduction of alkyl, vinyl, or aryl halides to the corresponding hydrocarbons using tin hydrides is one of the mildest and best-yielding methods for this important transformation. Although the general reaction is best demonstrated by reduction of simple substrates such as 4-bromotoluene[‌57‌] or 5-bromooctahydronaphthalen-1(2H)-one (5),[‌83‌] the reduction can be successfully performed on complex substrates, such as the penicillin derivative 7,[‌84‌] with excellent yields (Scheme 10). The stereoselectivity of this reaction is determined by the shape of the intermediate radical 8, and not by the stereochemistry of the starting bromide 7, which is employed as a mixture of two epimers. Hydrogen abstraction by 8 occurs on the less hindered exo-face of the cup-shaped radical. This example also shows that this method can tolerate a wide range of functional groups (for example, the hydroxy group does not require protection). Note also that the C—S bonds are not cleaved because the C—Br bond undergoes much more rapid homolytic cleavage.[‌66‌]

Meeeee 88 Meeeeeeee ee M—Me Meeee eeee Mee Meeeeeee[‌88‌,‌88‌,‌88‌]

Mee eeeeeeeeeeeeeeee ee eeee eeeeeeee ee eeeeeee eeeeeeeeeeee ee eee eeeeeeeee eeeeeeeee ee e M—Me eeee ee eee eeeeeeee ee e M—Me eeee ee 8-eeeee-8-eeeeeeeeeeeee[8.8.8]eeeeeee (8).[‌88‌] Meeeeeeeeee, eeeeeeeeeeeeeeee eee ee eeeeeeee eeee eeeee ee eee eeee eeeeeee ee eee eeeeeeee eeeeeeeee eeee eee eeeeeeee ee eee eeeeeeeee M—M eeeee eeeeee eeeeeeeeeeeee ee eeeee eeeeeeeee. Mee eeeeeeeee ee eeeeeeeeeee 88 eeee 8 eeeeeeeeeee ee eeeeeeeeeeeeeeee eeeeeee ee eeeeeeee ee eee M—Me eeeee α ee eee eeeeeeee eeeee, eeeeeeeeee eee eeeeeee eeeeeeeee ee eee eeeeeeee eeeeeeeeee ee eee eeeeeeee eeeee eeeeeeee eeee eeee ee e eeeeee eeeeeeee eeeeeee (Meeeee 88). Mee eeeeeee 88 ee eeee eeeeeeee eee ee eeeeeee eeeeeeeee eeee eee eeeeeeee eeeeeee 88.[‌88‌]

Me eeeeeee eeeeeee ee eeeeeeeee eeeeeeeee, eee eeeeeeeeee eeeeeee eeeee ee eeeeeeeee 88 (Meeeee 88) eee eeeeeeeeeee eeeeeee eeeee eee eeeeeee eeee eeeeee eeeeeeeeee; eeee ee eeeeeeee eeeeeee ee eee eeeeeee eeeeeeeeee ee eeeeeeeeee eeeeeee eeeeeeee.[‌88‌]

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Meeeee 88 Meeeeeeeeeeeeeee ee Mee Meeeeee Meeeeeeeee ee Meeeee—Meeeeee Meeee[‌88‌‌88‌]

Mee eeeeeeeeeeeeeeeee ee eee eeeeeee eeeeeeeeee ee eeeeeeeee eeee eeeeeee ee eee eeeeee (ee eeeeeee eeeeeeeeeeeeeee eeeeeeeeeee) eeeeee ee eee eeeeeeeeeeee eeeeee-eeeeeeee eeeeeeee. Meee, eeeeeeeee ee eeeeeeeeeeeeeeee eeee [(M)-8-eeeeeeeeeee]eeeeeee (88) eeee eeeeeeeeeeeeeeeee-e8 eeeee eeeeeee eeeeeeeeee eeeeeeeeeeee (±)-88.[‌88‌] Meeeeeee ee eeeeeeeeee eeeeeeeeee eeeee eeeeee eee eeeeeeee eeee eeeeeeee ee eeeeee eeeeeeeeeeeeeeeeeeee ee eeee.[‌88‌‌88‌]

Meeeee Meeee eeee eeeeeeeee eee ee eeee ee eeeeeeeeee eeeeeeeeee ee α-eeeeeeeeeee eeeeeeee eeeeeeeee.[‌88‌] Me eeeeeeeeeeee eeeeee ee 88% ee eeeeeeee ee eee eeeeeeeee ee eeeeeeee 88 ee eee eeeeeeee ee eeeeeeeee eeeeee eee eee eeeeee eeeeeeeeeeeeee 88 (Meeeee 88).[‌88‌] Meeeeeeeeeee ee eeeeee eeeeeeeee eee eeeeee Meeee eeeee eee eeee ee eeee.[‌88‌]

Mee eeeeeeeeeeeeeeeeeeee ee eee eeeeeeeee, ee eee eeeee eeee, eee ee eeeeeeeeeee eeeeeeeeee ee eeeeee eeeeeee eeeeeee eeeeeeeee ee eee eeeeeeee, ee eeeeeeeeeee eee eee eeee ee eee eeeeeeeeee eeeeeeee 8 (Meeeee 88). Meee eeeee eeeeeeee ee eeeeeeeeeeeeeeeeee eeeeeeeeee ee eeeee eeeeeee eee eeeeeeee eeee eeee eeeeeeee.[‌88‌,‌88‌‌888‌] Me eeeeeeeeee eeeeeeee ee eee eeeeee ee eeeeeeeee Meeee eeeee ee eee eeeeeeeeeeeeeeeeeeee ee eee eeeeeee eeeeeeeeee.[‌88‌,‌88‌,‌888‌‌888‌] Meeeeee eeeeeeeee ee eee α-eeee-β-eeeeeee eeeee 88 ee eeeeeeeeeeeeeeee ee eee eeeeeeeeeeee eeeee eee eeee-eeeeeee eeee-88, eeeeeee ee eee eeeeeeee ee e eeeeeeeee Meeee eeee, eee-88 ee eeeeee (Meeeee 88). Mee eeeeeeee eeeeeeeeeeeeeeeeeee eee ee eeeeeeeee ee eeeee ee eee eeeeeeeeee eeeeee eee eee eeeeeeee ee eeeeee eeee eeeeeee e eeeeee ee eeeeeeeeeeeeeeee eeeeeee.[‌888‌]

Meeeee 88 Meeeeeeeeeeeeeeee ee Meeeeeeeee ee Meeee Meeeeee eeee Meeeeeeee[‌88‌,‌88‌]

Meeeeee, ee e eeeeeeeeee eeeeeeeee, eee eeeeeeee eee ee eeeeeeeee eeeeeeeeeeeee eeee eee eeeeeeeeeeeee eee eeeeeeeee ee eeee eeeeeeeee eeee e eeeeeeeeeee ee ee eeeeeeeee eeeeeee.[‌888‌,‌888‌] Me eeeeeee ee eeee eeee ee eeeeeeee ee eee eeeeeeeee eeeeeeeee ee eeeeee 88 ee eeee eee eeeeeeeeeeeee eeeeeeeeeee eeeeeeeeee 88 (Meeeee 88).[‌888‌]

Meeeee 88 Mee ee e Meeeeeeee Meeeee ee e Mee Meeeeeee Me Meeeee e Meeeee—Meeeeee Meee[‌888‌]

Meeeeeeeeeee Meeeeeeee

Meeeeee (8); Meeeeee Meeeeeeee:[‌88‌]

MMMMMMM: Meeeeeee eeeeeeeeeeeeee eee eeeeee eeeeeeeeeee; eeee eee eeeeeeeeeee eeeeeeeeeee.

M eeeeeee ee eeee Me8MeM (88.8 eM, 888 eeee) eee 8-eeeeeeeeeeee (88.8 e, 888 eeee) ee e eeeeee eeeee eeeee eeeee eee eeeeeeeeee ee ee eeeee e 888-M eeee-eeeeeeee Me eeee. Meee eee eeeeeeee eee eeeeeeee (MM), eee eeeeeee eee eeeeeeeee ee eeeeeeeeeeee; eeeee: 8.8 e (88%); ee 888 °M.

Meeeeeeeeeeeeeeeeee-8(8M)-eee (8); Meeeeee Meeeeeeee:[‌88‌]

Me8MeM (8.88 e, 8 eeee) eee MMMM (8 ee) eeee eeeee ee e eeee ee eeeee eeeeeeee 8 (888 ee, 8.88 eeee) ee eee eeeeeee (888 eM) (MMMMMMM: eeeeeeeeee) eeeee M8. Mee eeeeeee eee eeeeeeee eee 88 e eee eeee eeeeee eee eeeeeeeeeeee eeeee eeeeeee eeeeeeee. Mee eeeee eeeeeee eee eeeeeeeee ee MeMM (88 eM) eee eeeeeeeee eeee eeeeee (8 × 88 eM) ee eeeeee eee eeeeeeee. Mee MeMM eeeee eee eeeeeeeeeeee ee eeee e eeeeeeeee eee; eeeee: 88 ee (88%).

(8eM,8M,8M,8eM)-8-(Meeeeeeeeeeee)-8-eeeeeeeeeeee-8M-eeeeeeeeee[e]eeeee-8-ee Meeeeee (88); Meeeeee Meeeeeeee:[‌888‌]

MMMMMMM: Meeeeeeeeeee eeeeeeee ee eeee eeeeeeeeee eee ee ee eeeeeeeeeeeeee ee eeee eeeeee ee eeeeeeee. Me ee ee eee eee eeee eeeeeeee, eee eeeee ee eeeee eeeeee eeeeee eeeeeeeee eee eeeee eee eeeeee eeeeee.

M eeee ee MeMM8 (8.8 ee, 8.888 eeee) ee MeMM (8.8 eM) eee eeeee eeee e eeeeeee ee e eeee ee eeeeee 88 (88 ee, 8.88 eeee) eee Me8MeMe (8.8 ee, 8.888 eeee) ee eeeeeeee MeMM (8 eM) ee 88 °M. Mee eeeeeee eee eeeeeeeeee eee 88 eee eeee e 888-M Me eeeeeeeeee eee eeee eeeeee eeee (88 ee, 8.8 eeee) eee eeeee ee eeeeeee eee eeeeeeeee Me8MeM eeee eee eeeeeeeeeeeee eeeee. Mee eeeeeee eee eeeeeee eee 8 eee, MM8Me8 eee eeeee, eee eee eeeeeeeee eeeeeee eee eeeeee eeee eee. ee MeMMM8. Mee eeeeeee eeeee eee eeeeeeeee, eeeee (MeMM8), eee eeeeeeeeeeee ee eeee ee eee, eeeee eee eeeeeeee ee eeeeee eeeeeeeeeeeeee [eeeeeee (MMMMMMM: eeeeeeeeee)/Me8M 8:8]; eeeee: 88 ee (88%).

References


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