Proposed is at total synthesis of the steroid desogestrel, utilizing a 1,4-addition/alkylation reaction to install the correct stereochemistry at C₈, C₁₃ and C₁₄ in a single-pot operation as well as to domino reaction to construct the B and C-steroid rings in a single operation. Detailed is the synthesis of a number of 1,4-addition precursors including the optimization of an achiral Z-allylic phosphonate and the subsequent 1,4-addition reactions of these compounds. It was discovered that, whilst a Z-allylic phosphonate took part in the 1,4-addition/alkylation as expected, the reaction with the E-double bond isomer afforded a 2 : 1 mixture of the 1,4-addition/alkylation product : an intramolecular-cyclization bicyclic heptanone product. This intramolecular-cyclization reaction has plagued the 1,4-addition/alkylation reactions with phenyl allyl sulfoxide, and this discovery enabled the reaction to be conducted successfully within the allylic sulfoxide series by employing a Z-allylic sulfoxide. Also detailed are the subsequent reactions to convert the 1,4-addition/alkylation products into the domino cyclization precursors and the attempted domino reactions of these compounds. Whilst the domino reaction could not be realized, the C-ring cyclization was found to be extremely successful in the phosphonate series and subsequent optimization enabled yields of up to 92% to be obtained.