Non-naturally occurring microbial organisms and related methods, processes and materials are for microbial organisms that include a genetic modification which enhances production of 3-hydroxybutanal or a downstream product of 3-hydroxybutanal such as 1,3-butanediol from endogenous central metabolic intermediates such as acetyl CoA or pyruvate which are converted to acetaldehyde. Two molecules of acetaldehyde are condensed to form the 3-hydroxybutanal using an aldolase capable of accepting acetaldehyde as both the acceptor and donor in an aldol condensation. The aldolase may be a deoxyribose phosphate aldolase type enzyme, and is typically introduced into the organisms. Energetically favorable pathways produce 3-hydroxybutanal or downstream products thereof.