(Arene)chromium tricarbonyl complexes in organic synthesis: stereoselective synthesis of cis- and trans-7-hydroxycalamenenes

Benzylic Activation and Stereochemical Control in Reactions of Tricarbonyl(arene)chromium Complexes

“…(106,107) Similarly, the 4-exo-isopropyl derivative 36 provides the corresponding endo alcohols upon treatment with hydride or MeLi. (102,103) Although the addition of crotylmagnesium chloride to ( --tetralone)chromium complex 37 is a stereoselective exo-addition with respect to the Cr(CO) 3 fragment, it is nonselective for the generation of new stereogenic centers in the crotyl fragment. However, in the presence of one equivalent of triethylaluminum, one diastereomer is obtained predominantly (Eq.…”

Enantioselective Isomerization of Allylic Alcohols Catalyzed by a Rhodium/Phosphaferrocene Complex

“…We have applied the Rh + / 1 -catalyzed enantioselective isomerization process to the first asymmetric synthesis of carboxylic acid 4 , which has served as a key intermediate in racemic syntheses of 7-hydroxycalamenene ( 5 ) and 7-hydroxycalamenenal ( 6 ), , two naturally occurring sesquiterpenes in the cadinene family . Thus, catalytic asymmetric isomerization of 2 by Rh + /(+)- 1 furnishes aldehyde (+)- 3 in 82% ee (87% yield; Figure ) .…”

Ionic and Organometallic‐Catalyzed Organosilane Reductions

“…Since the organosilane reduction of benzyl alcohols to the corresponding toluene derivatives is known, it is not surprising that the reduction of an aryl aldehyde to a toluene is possible. This transformation has been carried out with Et 3 SiH/TFA, 69,351,352 (EtO) 3 SiH, and Et 3 SiH with various catalysts, 353 Et 3 SiH/(C 6 F 5 ) 3 B, 281 PMHS/Pd/C, 316 and PMHS/ (C 6 F 5 ) 3 B. 354 The last combination also reduces alkyl aldehydes to the corresponding alkanes (Eq.…”