On the Stereochemistry of the Reduction of Cyclic Ketones with Lithium Tri-t-butoxyaluminum Hydride

Deuterium Isotope Effects in the Reduction of Cyclohexanones. The Concepts of Steric Approach Control and Product Development Control

“…Although masked by the secondary isotope effects, it is clear that if the secondary effects are able to overshadow the primary effect, then the primary effect itself must be very small, probably less than 2. This small value is certainly consistent with an early transition state as required by other explanations of product ratios (3)(4)(5); it is also equally consistent with a very late transition state, where the hydrogen has been substantially transferred. Other possible reasons for a very small isotope effect concern the nature of the reaction and the geometry of the transition state itself.…”

“…It is precisely this point which sets this explanation apart from others, which postu!ates an early transition state for all cases (3)(4)(5). The test of the Dauben hypothesis thus becomes one of evaluating the extent of bond breaking and bond making in the transition states of reduction of ketones with varying steric hindrance and determining whether or not there is a transition state shift.…”

“…1). Various suggestions as to the basis of this striking stereochemical dependence have been offered (1,(3)(4)(5). Fifteen years ago, in a paper which has now become a classic in this area of hydride reductions, Dauben et al (1) put forward the first explanation and introduced the terms steric approach control and product development control.…”

Synthèse et propriétés de la tert-butyl-5 diméthyl-3,3 cycloheptanone

“…I1 apparaissait inttressant, dans le cadre de nos travaux sur la stCrtochimie des additions sur des systkmes cycliques (8), de determiner si l'introduction sur la tert-butyl-5 cycloheptanone d'un groupe gemdimtthyle en position 3 provoquerait lors de la rtduction de cette moltcule (la) une stCrtosClectivitt plus Clevte que celle observCe lors de la rkduction (6,7) de la tert-butyl-4 cycloheptanone non substituCe (lb). Les rtsultats obtenus lors de la synthkse et de la riduction de l a font l'objet du prtsent travail.…”

STEREOCHEMISTRY OF THE REDUCTION OF CYCLIC KETONES WITH THE PYRIDINE-n-BUTYLHTHIUM ADDUCT: STERIC APPROACH AND PRODUCT DEVELOPMENT CONTROLS

“…Very similar ratios were obtained when lithium aluininiuin hydride (3) and lithium tri-t-butoxyaluminium hydride (2) were used. I t has been proposed (2) For personal use only. these two reagents can be accounted for on the basis of steric factors alone ("steric approach control") and not of "product development control" (4).…”