91Ó°ÊÓ

The given compound (a) is 2-(4-oxopentyl)cyclohexan-1one (1,5-diketone), which undergoes intramolecular aldol additions to form a stable six-membered ring, forming the 1-(7a-hydroxyoctahydro-1H-inden-1-yl)which is a$\mathrm{β}$-hydroxyketone.

The formation of $\mathrm{β}$-hydroxyketone1-(7a-hydroxyoctahydro-1H-inden-1-yl) is shown as follows:

Formation of 1-(7a-hydroxyoctahydro-1H-inden-1-yl) (a)

The given compound (b) is cyclodecane-1,6-dione (1,6-diketone) whichcan potentially make either asevenor a five-membered ring productthrough intramolecular aldolcondensation.

A more stableproduct, the one with the five-membered ring, is the only product of thereaction, thusforming 7a-hydroxyoctahydro-4H-inden-4-one.

The formation of 7a-hydroxyoctahydro-4H-inden-4-one is shown as follows:

Formation of 7a-hydroxyoctahydro-4H-inden-4-one (b)

The given compound (c) is heptanedial(1,5-diketone), which undergoes intramolecular aldol additions to form a stable six-membered ring, forming the 2-hydroxycyclohexane-1-carbaldehyde ($\mathrm{β}$-hydroxyketones).

The formation of $\mathrm{β}$-hydroxyketone2-hydroxycyclohexane-1-carbaldehyde is shown as follows:

Formation of 2-hydroxycyclohexane-1-carbaldehyde (c)

The given compound (d) is 2-(3-oxobutyl)cyclohexan-1-one (1,6-diketone),whichcan potentially make either aseven or a five-membered ring productthrough intramolecular aldolcondensation.

A more stable product, the one with the five-membered ring, is the only product of the reaction,thus forming 8a-hydroxyoctahydronaphthalen-2(1H)-one.

The formation of 8a-hydroxyoctahydronaphthalen-2(1H)-one is shown as follows:

Formation of 8a-hydroxyoctahydronaphthalen-2(1H)-one (d)